U  W  O  13        u  I  u*  i\  r%  i\ 


THE 
LIBRARY  OF  USEFUL  STORIES 


The  Great  Nebula  in  Andromeda. 
iEoderts.) 


STORIES  of  the  UNIVERSE 


The  Stars 

By 
GEORGE   F.  CHAMBERS,  F.R.A.S. 

OF    THE    INNER    TEMPLE,    BARRISTER-AT-LAW 

AUTHOR    OF 

■'a    handbook    of    DESCRIPTIVE   AND    PRACTICAL   ASTRONOMY," 

"pictorial   ASTRONOMY,"    ETC. 


WITH  MANY  ILLUSTRATIONS 


NEW    YORK 

Review  of  Reviews   Company 
1909 


Copyright,  1895, 
By  D.   APPLETON  AND  COMPANY, 


PREFACE. 


When  invited  to  write  this  little  book,  I  was  asked  so> 
to  shape  it  that  it  should  be  a  concise  but  readable  out- 
line of  that  branch  of  knowledge  which  one  associates 
with  the  expression  the  "  Starr}^  Heavens  "  liberally  inter- 
preted. I  was  to  cater  for  those  rapidly  growing  thou- 
sands of  men  and  women  of  all  ranks  who  are  manifesting 
in  these  closing  years  of  the  nineteenth  century  in  sO' 
many  ways  and  in  so  many  places  an  interest  in  the  facts 
and  truths  of  Nature  and  Physical  Science.  The  task 
thus  imposed  upon  me  was  a  very  congenial  one,  and  I 
gladly  undertook  it.  How  far  I  have  succeeded  in  pre- 
senting my  facts  in  a  bright  and  cheery  spirit  others  must 
determine.  But  I  would  ask  it  to  be  understood  that  I 
have  dealt  with  facts  rather  than  fancies.  There  are  too 
many  of  the  former  available  for  a  writer  on  astronomy  to 
make  it  worth  while  to  waste  space  in  dealing  with  the 
latter. 

This  volume  will  shortly  be  followed  by  another  in  the 
same  unconventional  style  entitled,  "  The  Story  of  the 
Solar  System  ;  or.  The  Sun,  Planets,  and  Comets  popularly 
described."  I  trust,  however,  that  many  of  my  readers 
will  not  be  content  with  these  mere  outlines  of  a  noble 
science,  but  will  desire  to  obtain  a  more  complete  grasp 
of  the  subject  in  all  its  bearings  by  studying  first  my 
"  Pictorial  Astronomy  "  (Whittaker  &  Co.,  2nd  ed.),  and 
then  my  "  Handbook  of  Astronomy  "  (Clarendon  Press, 


6  PREFACE. 

4th  ed.,  3  vols.),  which  is  a  comprehensive  treatise,  yet 
written  in  popular  language  and  form  so  as  to  subserve 
the  wants  of  general  readers.  From  both  these  works 
thoughts  and  ideas  have  no  doubt  found  their  way  into 
the  present  volume. 

For  the  chapter  on  the  work  of  the  Spectroscope  in 
connection  with  the  stars  I  am  indebted  to  my  friend  Mr. 
E.  W.  Maunder,  of  the  Royal  Observatory,  Greenwich, 
one  of  the  highest  living  authorities  on  this  branch  of 
astronomy.  G.  F.  C. 

NORTHFIELD  GRANGE,  EAST  BOURNE, 

December^  1894. 


CONTENTS. 


CHAPTER  PAGE 

I.  Introductory  Thoughts      ....  9 

II.   First  Experiences  of  a  Starlight  Night  .  ii 

III.  The   Brilliancy    and    Distances    of   the 

Stars 21 

IV.  The   Grouping  of   the   Stars  into  Con- 

stellations         28 

V.   The  History  of  the  Constellations        .  39 

VI.   The  Number  of  the  Stars  ....  43 

VII.  Double  Stars 51 

VIII.  Family  Parties  of  Stars     ....  59 

IX.  Coloured  Stars 62 

X.   Moving  Stars 67 

XI.   Temporary  Stars 75 

XII.  Variable  Stars 83 

XIII.  The  Stars  in  Poetry 95 

XIV.  Groups  of  Stars loi 

XV.   Clusters  of  Stars 106 

XVI.   Nebula 114 

XVII.   The  Milky  Way 129 

XVIII.  The    Spectroscope   and    the    Stars    and 

Nebula 137 

APPENDIX    I.   Table  of  the  Constellations      .  150 
"            II.   List    of    Celestial    Objects   for 

Small  Telescopes      .        .        .  153 

INDEX 157 


LIST   OF   ILLUSTRATIONS. 


JFIG. 

PAGE 

I. 

The  Great  Nebula  in  Andromeda     .         Frontispieci 

2. 

The  Points  of  the  Compass 

. 

20 

3- 

Ursa  Major  and  Polaris     . 

31 

4- 

Orion 

43 

5- 

a  Plerculis  (double  star) 

51 

•6. 

C  Ilerculis  (1865)      . 

54 

7- 

C  Herculis  (1871) 

»       54 

8. 

i  Herculis  (1883) 

55 

9- 

€  Lyrce 

60 

lO. 

(T  Orionis  . 

60 

II. 

0  Orionis  . 

61 

12. 

The  Pleiades     . 

104 

13- 

13  M.  Herculis 

107 

14. 

5  M.  Librae     . 

.     loq 

15. 

80  M.  Scorpii   . 

no 

J6. 

67  M.  Cancri    . 

112 

17. 

77  M.  Ceti  (nebulous  star) 

113 

18. 

The  Ring  Nebula  in  Lyra  (Sir  J.  Herschel)     . 

116 

19. 

The  Ring  Nebula  in  Lyra  (Earl  of  Rosse) 

116 

20. 

The  Nebula  43  W  I.  Virginis    .... 

117 

21. 

The  Spiral  Nebula  51  M.  Canum  Venaticorum  (Sii 

J.  Herschel) 

118 

22. 

The  Spiral  Nebula  51  M.  Canum  Venaticorum  (Ear 

of  Rosse) 

119 

23- 

The  "Owl"  Nebula  in  Ursa  Major  . 

,     120 

24. 

The  "Omega"  Nebi 

ila  in 

Scut 
8 

um  S 

obies 

kii      . 

.     126 

CHAPTER   I. 

INTRODUCTORY   THOUGHTS. 

"  By  the  word  of  the  Lord  were  the  heavens  made  ;  and  all  the 
host  of  them  by  the  breath  of  His  mouth."—  Psalm  xxxiii.  6. 

No  great  while  ago  a  defendant  who  had  to  appear  at 
a  Court  held  at  Carlisle  arrived  there  true  to  his  time  ac- 
cording to  the  local  time  at  Carlisle  appointed  by  the  Court 
for  the  sitting ;  but  he  found  that  the  Court  had  met  by 
Greenwich  time,  and  in  his  absence  had  decided  the  case 
against  him.  This  was  considered  by  certain  gentlemen 
"  learned  in  the  law  "  to  be  both  a  hardship  and  an  illegal- 
ity, and  the  poor  man  obtained  a  second  chance  of  being 
heard.  Subsequently  to  this  incident  Parliament  passed 
an  Act  providing  that  whenever  any  expression  of  time 
occurs  in  any  Act  of  Parliament,  deed,  or  other  legal  in- 
strument, the  time  referred  to  shall  (unless  it  is  otherwise 
specifically  stated)  be  held,  in  the  case  of  Great  Britain,  to 
be  Greenwich  mean  time,  and  in  the  case  of  Ireland,  to  be 
Dublin  mean  time. 

Quite  recently  the  following  incident  occurred  a.  Liver- 
pool, the  outcome  of  which,  by  the  way,  seems  hardly 
consistent  with  the  statute  just  referred  to.  A  levy  was 
made  by  the  Sheriff's  Order  on  the  household  goods  of 
some  person  who  urged  that,  as  this  was  done  after  sun- 
set, it  was  illegal.  The  Director  of  the  Liverpool  Observa- 
tory being  called  to  testify  to  the  time  of  sunset  on  the  day 
of  the  levy,  the  defendant's  objection  was  upheld.  The 
conclusion  appears  unavoidable  that,  in  noting  the  times 
of  sunrise  and  sunset,  local  time,  and  not  Greenwich  time. 


lO  THE  STORY  OF  THE  STARS. 

must  be  regarded.  This,  as  I  have  said  above,  seems  not 
to  be  consistent  with  the  statute,  but  I  am  not  concerned 
here  to  discuss  the  question  in  that  aspect.  I  only  want 
to  use  the  facts  referred  to  as  a  means  of  showing  that 
there  is  something  more  in  the  study  of  the  stars  than 
many  persons  imagine.  In  other  words,  that  in  inviting 
my  readers  to  give  a  Httle  thought  to  astronomical  mat- 
ters, I  am  asking  them  to  consider  things  which  are  not 
only  not  necessarily  occult,  difficult,  or  fanciful,  but  which 
have  in  one  way  or  another  no  slight  bearing  on  business 
and  pleasures  of  life. 

It  is  not  necessar}'  to  develope  the  argument  to  any 
great  length,  but  it  is  just  worth  a  passing  thought,  in  con- 
sidering the  question  whether  astronomy  has  any,  and  if 
so  what,  utilitarian  value,  to  remember  that  those  two  ob- 
jects of  daily  interest  and  use,  the  almanack  and  the  diary, 
entirely  depend  for  their  existence  on  the  labours  of  the 
astronomer  in  his  obser\'ator)'.  In  our  case,  as  English- 
men, these  books  are  based  on  the  labours  of  certain  very 
insufficiently  paid  members  of  her  Majesty's  Civil  Service 
at  the  Royal  Observatory,  Greenwich,  and  at  the  Nauti- 
cal Almanack  office  in  Gray's  Inn  Road,  Were  the  staff 
belonging  to  either  establishment  to  resort  to  the  fashion- 
able expedient  of  a  strike  for  higher  pay  (and  there  would 
be  much  justification  for  their  doing  so),  sooner  or  later 
all  the  almanacks  and  diaries  would  cease  to  be  published, 
and  the  public  business  of  the  country  would  to  a  large 
extent  come  to  a  standstill.  But  this  is  not  all.  The 
shipping  of  England  would  come  to  a  standstill,  or  nearly 
so,  and  that  not  figuratively,  but  literally.  Our  vessels 
would  have  to  go  back  to  the  principles  of  navigation 
practised  by  the  inhabitants  of  these  islands  2000  years 
ago  ;  they  would  have  to  become  coasting  vessels,  feeling 
their  way  from  place  to  place,  and  chiefiy  by  daylight. 
Long  voyages  oversea  would  be  well-nigh  impossible,  or 


FIRST  EXPERIENCES  OF  A  STARLIGHT  NIGHT,    ii 

only  to  be  executed  in  the  face  of  the  greatest  risks  and 
the  wildest  chance.  Our  railway  system  would  become 
utterly  disorganised.  A  few  trains  could  run,  but  the  in- 
tervals between  them  would  have  to  be  considerable,  and 
they  could  only  travel  by  daylight  and  at  very  low  speeds. 
These  general  thoughts  will,  I  trust,  serve  as  a  suffi- 
cient preliminary  proof  that  there  is  more  in  the  "  Story  of 
the  Stars  "  than  lies  upon  the  surface  of  things. 


CHAPTER  II. 
FIRST   EXPERIENCES   OF  A   STARLIGHT   NIGHT. 

Let  us  suppose  a  would-be  observer  of  the  stars  to 
station  himself  on  some  fine  evening  soon  after  sunset  in 
an  open  and  if  possible  elevated  position.  A  varied  and 
striking,  not  to  say  picturesque,  spectacle  would  soon  un- 
fold itself  to  his  gaze.  Stars  invisible  during  the  daytime, 
because  their  light  was  overcome  by  the  superior  light  of 
the  sun,  would  soon  appear.  They  would  become  visible  at 
first  only  one  by  one,  as  it  were ;  then  several  would  seem 
to  start  into  being,  and  finally  their  number  would  increase, 
until  it  might  be  supposed  that  many  thousands  were  visi- 
ble, though  in  point  of  actual  fact  no  more  than  about 
3000  stars  at  the  outside  can  ever  be  seen  by  the  naked 
eye  at  any  one  time  or  place. 

An  attentive  scrutiny,  prolonged  in  one  case  for  an 
hour  or  two,  and  in  another  case  for  a  day  or  two,  will 
disclose  a  twofold  fact :  first,  that  all  the  objects  assumed 
to  be  stars  are  moving  in  a  body  over  the  face  of  the  sky 
from  hour  to  hour,  whilst  two  or  three  brighter  ones  are 
to  be  noticed  which  not  only  participate  in  the  constant 
movement  from  hour  to  hour  of  the  whole  mass,  but  have 
an  individual  motion  of  their  own  in  virtue  of  which  either 


12         THE  STORY  OF  THE  STARS. 

from  day  to  day,  or  in  other  cases  from  week  to  week, 
they  will  be  noticed  to  change  their  relative  positions  with 
respect  to  the  twinkling  stars  around  them.  Pausing  for 
a  moment  to  distinguish  between  these  two  classes  of 
celestial  objects,  it  may  be  stated  that  the  bodies  which 
twinkle,  and  have  (seemingly)  no  relative  movement,  are 
the  "  fixed  stars,"  properly  so  called  ;  whilst  the  others,  it 
may  be  only  two  or  three  in  number  on  any  given  even- 
ing, and  which  do  not  twinkle,  are  objects  of  a  totally  dis- 
tinct character,  and  known  as  "  planets." 

Taking  the  sky  as  a  whole,  with  its  2000  or  its  3000 
naked-eye  stars,  the  observer  (if  in  a  northern  latitude) 
will  notice,  if  he  turns  his  back  to  the  south,  remembering 
where  the  sun  was  at  mid-day,  that  after  successive  inter- 
vals, say  of  a  J  of  an  hour,  new  stars  are  presenting  them- 
selves on  the  right,  rising  above  the  horizon.  If  he  will 
follow  some  one  group  in  particular  far  into  the  night,  he 
will  find  that  it  gradually  rises  in  the  heavens  in  the  direc- 
tion from  east  to  west.  After  a  certain  interval  it  ceases 
to  rise  higher ;  then  descends  on  his  left,  and  finally  dis- 
appears below  the  western  horizon.  This  onward  march 
is  not  an  attribute  of  all  the  stars  quite  in  the  simple  form 
thus  mentioned,  for  of  some  of  them  it  must  be  said  that 
they  do  not  rise  above  the  horizon  nor  sink  down  below 
it,  because  they  are  always  above  it.  Such  are  the  stars 
which  face  our  observer,  who  with  his  back  to  the  south 
is  looking  towards  the  north.  Of  the  stars  thus  circum- 
stanced there  are  some  which  seem  to  describe  a  pathway 
which  scrapes,  as  it  were,  the  northern  horizon ;  whilst 
others  seem  to  describe  circular  paths,  which  become 
more  and  more  contracted  towards  a  certain  star  in  par- 
ticular. That  star  seems  almost  motionless  throughout 
the  entire  night,  and  is  known  as  the  "  Pole  Star."  The 
stars  which  are,  as  above  stated,  always  above  the  hori- 
zon, would  always  be  visible  during  the  whole  24  hours 


FIRST  EXPERIENCES  OF  A  STARLIGHT  NIGHT.    13 

were  it  not  for  the  sunlight.  As  a  matter  of  fact,  indeed, 
the  larger  of  them  can  on  any  fine  day  be  traced  by  means 
of  a  large  telescope  round  and  round  during  the  whole  24 
hours  day  after  day  throughout  the  year,  weather  permitting. 
The  movement  of  the  heavens  which  has  just  been  re- 
ferred to  is  commonly  called  the  "diurnal  movement."  A 
better  conception  of  it  perhaps  may  be  had  if  we  imagine 
(as  indeed  the  ancients  did)  that  we  are  in  the  centre  of  a 
literal  sphere ;  that  the  stars  are  attached  to  the  interior 
surface  of  such  a  sphere ;  and  that  it  is  endued  from  with- 
out with  a  rotatory  motion  once  in  ever}-  period  of  time 
which  we  designate  a  day  of  24  hours.  Regarding  the 
universe  thus,  we  must,  by  one  more  forward  stretch  of 
the  imagination,  consider  the  heavens  to  be  always  revolv- 
ing around  an  invisible  axis  called  the  axis  of  the  world, 
which  passes  through  the  place  of  observation  and  a  par- 
ticular point  near  to  the  Pole  Star.  The  direction  of  mo- 
tion will  be  from  east  to  west ;  and  whilst  for  us  in  Eng- 
land the  visible  polar  point  of  this  imaginary-  axis  will  be 
the  North  Pole,  the  other  end  of  the  axis  will  be  pointing 
in  the  opposite  direction  to  another  point  called  South 
Pole.  For  the  reader  to  obtain  a  full  and  true  realisation 
of  these  statements,  which  in  the  abstract  no  doubt  have 
a  visionary  sound,  he  must  take  a  voyage  to  the  Southern 
hemisphere — say,  to  the  Cape  of  Good  Hope  or  Australia. 
Doing  this,  he  will  come  face  to  face  with  a  condition  of 
things  which  at  first  sight  may  be  a  little  puzzling.  He 
will  have  lost  both  the  North  Pole  and  the  Pole  Star,  and 
also  the  constellation  of  the  Great  Bear  and  other  constel- 
lations which  we  associate  with  the  north,  and  will  find 
himself  called  upon  to  study  a  very  different  situation.  In 
>jrder  to  discover  a  polar  point  he  will  have  to  face  the 
south  instead  of  the  north  ;  he  will  find  no  bright  star  at, 
or  anywhere  near,  the  South  Pole ;  and  no  Great  Bear  to 
recall  the  memories  of  childhood  and  the  nursery. 


14  THE  STORY  OF  THE  STARS. 

The  remarks  in  the  preceding  paragraph  will  have 
paved  the  way  for  the  statement  which  must  now  be  made, 
that  the  study  of  the  stars  as  regards  their  location  in  the 
heavens  is  intimately  mixed  up  with  terrestrial  questions 
of  geography  ;  in  other  words,  that  the  observer's  oppor- 
tunity of  surveying  the  fields  of  view  afforded  by  the 
heavens  ever  depends  upon  the  latitude  (not  the  longitude) 
of  his  place  of  observation  on  the  earth.  Wherever  he 
may  be,  provided  he  be  not  immediately  at  the  equator  or 
pole,  he  will  have  to  consider  the  heavens  as  comprising  3 
distinct  regions,  each  with  its  own  particular  peculiarities. 
The  first,  bounded  by  an  imaginary  circle  called  the  "  cir- 
cle of  perpetual  apparition  " ;  the  second,  bounded  by 
another  imaginary  circle  called  the  "circle  of  perpetual 
occultation  " ;  the  third  being  all  the  area  not  embraced 
by  either  of  the  others.  All  the  stars  lying  between  the 
first  circle  and  the  visible  pole  will  be  perpetually  visible 
to  our  observer  throughout  the  year,  barring  of  course 
accidents  of  sunshine  or  weather.  All  the  stars  lying  be- 
tween the  second  circle  and  the  opposite  (or  invisible)  pole 
will  be  perpetually  invisible  to  our  observer,  because  none 
of  them  rise  above  his  horizon.  This  is  the  condition  of 
things  as  regards  an  observer  in  the  Northern  hemisphere. 
Looked  at  on  the  other  hand  from  a  station,  say  in  Aus- 
tralia, the  converse  of  the  foregoing  will  be  the  condition 
of  things.  The  stars  perpetually  visible  in  England  will 
be  perpetually  invisible  in  Australia,  and  the  stars  perpet- 
ually out  of  view  in  England  will  be  perpetually  in  view  in 
Australia.* 

The  reader  will  by  this  time  quite  understand  that 

*  The  statement  in  the  text  will  only  be  absolutely  and  literally 
true  when  the  stations  between  which  the  comparisons  are  made  are 
in  identical  latitudes,  the  one  north  and  the  other  south.  For  in- 
stance, it  would  be  about  true  of  Dunedin,  New  Zealand,  and 
Geneva  in  Switzerland. 


FIRST   EXPERIENCES  OF  A  STARLIGHT  NIGHT.   15 

■when  we  talk  about  the  celestial  sphere,  or  the  vault  of 
heaven,  or  the  axis  of  the  world,  or  the  poles,  we  are  re- 
sorting to  pure  abstractions  which  are  only  calculated  to 
convey  in  a  crude  fashion  ideas  of  apparent  movements 
which  it  is  difficult  to  describe  in  words,  or  to  indicate  by 
pictures,  or  to  reproduce  in  model  with  mechanical  appli- 
ances. It  may,  however,  be  said  that  a  pair  of  globes  in- 
telligently studied  may  be  of  some  service.  Perhaps  it  is 
worth  while  to  note  in  passing  that  ideas  and  expressions 
on  this  subject  which  we  employ  simply  as  figures  of 
speech,  were  made  use  of  by  the  astronomers  of  antiquity 
in  a  literal  and  material  sense.  Many  of  them  fully  be- 
lieved in  the  existence  of  a  solid  celestial  vault  with  a  ma- 
terial axis  provided  with  pivots  turning  in  fixed  sockets, 
the  stars  being  fastened  to  the  surface  of  the  vault  by 
nails  or  such-like  attachments.  Vitruvius  may  be  men- 
tioned as  one  of  the  best-known  writers  of  antiquity  who 
has  recorded  as  facts  ideas  of  this  sort. 

It  would  not  be  in  accordance  with  the  design  of  this 
little  work  to  go  very  deeply  into  matters  of  the  kind 
brought  under  the  reader's  notice  in  the  pages  immedi- 
ately preceding.  Suffice  it  then  to  add  that  whilst  the 
longitude  of  an  observer's  position  has  nothing  to  do  with 
the  question  of  whether  he  sees  some  stars  and  not  others 
on  any  given  night,  it  has  a  good  deal  to  do  with  the  ques- 
tion of  what  stars  are  visible  at  any  given  moment  of  time 
to  an  American  at  New  York,  to  an  Englishman  in  Lon- 
don, or  to  a  Hindoo  at  Calcutta.  For  instance,  when  a 
Londoner  is  going  to  bed  at  the  hour  of  11  p.  m.,  the 
New  Yorker  will  be  sitting  down  to  his  dinner  at  6  p.  m., 
whilst  the  Calcutta  Hindoo  will  be  preparing  for  breakfast. 
The  difference  of  1 1  hours  of  absolute  time  which  exists 
between  New  York  and  Calcutta  will  result  in  each  of 
those  places  having  a  totally  different  batch  of  constella- 
tions presented  to  its  gaze ;  because  London  occupies  an 


1 6  THE  STORY  OF  THE  STARS. 

intermediate  position,  the  Londoner  will  see  certain  stars 
over  his  head  which  to  the  Calcutta  Hindoo  will  appear 
setting  near  the  W.  horizon,  and  which  to  the  New 
Yorker  will  appear  low  down  in  the  E.  horizon,  just 
rising. 

Whilst  it  is  intended  as  far  as  possible  to  exclude  from 
this  volume  matters  of  mathematics  and  geometry,  there 
are  a  few  such  matters  which  must  be  stated  to  and  be 
comprehended  by  the  reader  if  he  would  follow  up,  to  any 
good  purpose,  the  study  of  astronomy  as  a  pleasant  and 
profitable  occupation. 

We  sometimes  have  to  speak  of  a  body  being  in  a 
"  vertical  "  position.  This  means  "  upright,"  and  a  heav- 
enly body  is  in  a  vertical  position  when  it  is  exactly  over 
the  observer's  head.  The  vertical  of  a  place,  then,  is  the 
direction  from  which  a  body,  set  free  to  fall  as  it  will, 
seems  to  come  when  it  strikes  the  earth  at  the  place.  It 
is  indicated  by  the  direction  of  a  string  made  fast  at  one 
extremity,  whilst  the  other  extremity  supports  a  weight  of 
some  kind.  Such  a  combination  constitutes  a  plumb-line, 
and  is  used  by  masons  and  bricklayers  for  the  express 
purpose  of  ensuring  the  uprightness  or  verticality  of  their 
work.  Further,  it  may  be  stated  that  the  vertical  of  a 
place  is  constantly  perpendicular  to  the  surface  of  water 
there  which  is  at  rest. 

The  imaginary  point  in  the  sky  where  the  vertical  pro- 
longed from  the  ground  upwards  meets  the  celestial  vault 
is  the  "  zenith  "  of  the  place  of  observation.  It  is  of 
course  the  point  exactly  above  the  observer's  head.  If 
one  could  conceive  the  vertical  prolonged  downwards 
through  the  earth  and  coming  out  on  the  other  side,*  and 

*  The  following:  "  anecdote  "  illustrates  this  :  An  American  in- 
quired of  as  to  the  suitability  of  a  certain  soil  for  growing  carrots, 
said  that  they  grew  so  well  in  it  that  the  roots  reached  right  through 
to  the  other  side  of  the  earth,  where  people  stole  the  carrots  by  pull- 


J 


FIRST  EXPERIENCES  OF  A  STARLIGHT  NIGHT.   17 

carried  forwards  till  it  met  the  celestial  sphere  at  another 
point,  it  would  do  so  at  a  point  which  is  called  the  "  nadir  " 
of  the  observer  on  the  upper  side,  so  to  speak,  of  the  earth. 
An  observer  standing"  out  on  an  open  plain,  or  better  still 
in  a  boat  on  the  open  sea,  will  notice  that  his  view  of  the 
land  in  the  one  case,  and  of  the  sea  in  the  other,  is  cut  off 
from  the  sky  by  a  circular  boundary  line,  he  himself  being 
in  the  centre  of  the  circle.  This  circle  is  called  the 
'*  horizon."  It  really  is  a  horizontal  plane  passing  through 
the  place  of  observation  at  right  angles  to  the  vertical. 

The  "  plane  of  the  meridian  "  of  a  place  is  an  imagi- 
nary plane  passing  through  what  we  have  spoken  of  as  the 
axis  of  the  heavens  and  the  vertical  of  the  place.  Suitable 
observation  shows  that  the  uppermost  and  lowermost 
points  in  the  circles  seemingly  described  by  all  the  stars 
are  situated  in  this  plane.  The  intersection  of  this  plane 
of  the  meridian  with  the  horizon  to  the  north  and  to  the 
south  constitutes  what  we  call  the  "meridian  line,"  or 
simply  the  "  meridian  "  of  the  place  of  observation.  What 
it  is  and  what  it  means  will  perhaps  best  be  grasped  by  a 
consideration  of  the  original  meaning  of  the  word.  It 
comes  from  2  Latin  words,  through  a  single  Latin  word, 
the  words  of  origin  being  medins  middle,  and  dies,  day — 
meaning  in  effect  the  point  of  the  horizon  immediately  be- 
low the  place  in  the  heavens  where  the  sun  is  when  it  has 
run  half  its  daily  course  from  sunrise  to  sunset. 

With  the  horizon  and  the  meridian  understood,  the 
cardinal  points,  north,  south,  east,  and  west  seem  to  come 
naturally.  An  observer  placed  in  the  direction  mentioned 
at  the  beginning  of  this  chapter,  that  is,  facing  the  Pole 
Star,  will  (in  England)  be  facing  the  North  ;  immediately 
behind  him  will  be  the  South  ;  whilst  on  his  right  will  be 

ing  them  through  by  the  tips^  instead  of  pulling  them  up   (as 
usually  done)  by  the  tops. 
2 


1 8  THE  STORY  OF  THE  STARS. 

the  East  and  on  his  left  the  West.  These  words  in  Eng- 
lish convey  very  little  to  us,  but  in  their  Latin  forms  are 
much  more  expressive.  The  Latin,  by  the  way,  reappears 
in  the  French.  For  instance,  the  Latin  for  "  North  "  is 
septejitrio,  which  recalls  the  7  {septeni)  stars  near  the 
North  Pole  ;  in  French  it  is  septentrion.  Then  the  South 
has  already  been  mentioned  and  reaches  us  in  French  as 
inzdz.  Then  the  East  is  orzens  (Fr.  Vorienf),  z.  e.,  the 
place  where  the  sun  rises.  And  the  West  is  occidens  (Fr. 
r Occident),  z.  e ,  the  place  where  the  sun  falls,  /.  e.,  sets. 

It  is  sometimes  necessary  to  consider  the  position  of  a 
star  or  the  distance  of  one  star  from  another  by  making  a 
measurement  or  an  estimate  along  the  plane  of  the  hori- 
zon, or  along  some  other  plane  parallel  thereto.  This  is 
spoken  of  as  a  measurement  in  "  azimuth  "  ;  or,  to  put  it 
in  another  way,  let  us  imagine  a  plane  passing  through 
the  zenith  and  through  any  star  whatever  ;  that  would  be 
at  the  moment  of  observation  the  azimuthal  plane  of  the 
star ;  and  the  angle  between  this  plane  and  the  plane  of 
the  meridian,  or  the  star's  distance  from  the  meridian  thus 
measured,  would  be  the  star's  "  azimuth  "  at  the  particular 
moment  when  the  observation  was  made. 

A  few  words  respecting  angular  distances  and  their 
measurement  seem  now  needed,  but  they  must  be  very 
general  because  the  study  of  angles  is  a  matter  which  con- 
cerns geometry  in  the  first  instance  and  astronomy  only  in 
a  secondary  sense. 

Every  circle  is  considered  to  be  divided  into  360  de- 
grees, every  degree  (°)  being  subdivided  into  60  minutes, 
and  every  minute  (')  into  60  seconds.  Formerly  every 
second  (")  was  divided  into  60  thirds,  but  this  method  of 
counting  has  become  quite  obsolete,  and  when  it  is  neces- 
sary, as  it  often  is,  to  deal  with  fractions  of  a  second,  re- 
sort is  had  to  decimals.  Occasions,  indeed,  sometimes 
arise  when  it  is  convenient  to  go  no  further  than  whole 


FIRST  EXPERIENCES  OF  A  STARLIGHT  NIGHT.    19 

minutes  and  to  express  as  decimals  of  a  minute  the  sec- 
onds which  we  wish  to  record.  Indeed,  on  occasions, 
even  the  minutes  and  seconds  taken  together  are  set  down 
as  simple  decimals  of  a  degree.  Thus,  45°  12'  20"  might 
be  expressed  as  45°  12'. ^3  or  45°.205. 

The  whole  circle  being  taken  at  360°,  a  half-circle  em- 
braces 180°  ;  a  quarter  circle,  or  "  quadrant,"  is  90°,  whilst 
the  eighth,  or  "octant,"  represents  45°.  An  intermediate 
subdivision,  a  sixth,  or  "sextant,"  furnishes  a  word  which 
has  an  astronomical  application,  but  it  is  to  an  instrument, 
and  not  to  the  space  which  the  word  suggests.  The 
words  "  octant  "  and  "  sextant  "  as  portions  of  a  circle  are 
not  in  use,  notwithstanding  that  the  words  themselves 
exist. 

Applying  to  the  circle  thus  divided  the  4  cardinal 
points  already  mentioned  we  obtain  the  divisions  which 
constitute  the  dial  of  the  "  mariner's  compass,"  and  an  at- 
tentive consideration  of  the  manner  in  which  that  is  di- 
vided will  pave  the  way  for  a  due  comprehension  of  the 
manner  in  which  angles  are  measured  for  astronomical 
purposes. 

It  will  be  seen  by  the  diagram  that  if  a  circle  is  divided; 
into  4  quadrants  we  are  furnished  with  the  4  principaU 
points,  N.,  E.,  S.,  and  W.  Each  quadrant  therefore  em- 
braces 90°  of  the  360°  which  constitute  the  entire  circle. 
Dividing  each  quadrant  into  two  halves  gives  us  the  sub- 
divisions known  as  N.E.,  S.E.,  S.W.,  and  N.W.  Each  of 
these  represents  the  half  of  90°,  or  45°.  Then  by  subdi- 
viding each  half-quadrant  into  half  again  we  obtain  what 
are  quarter-quadrants,  though  no  such  phrase  is  in  use. 
The  quarter-quadrants  give  us  the  points  known  as 
N.N.E.,  E.N.E.,  E.S.E.,  S.S.E.,  S.S.W..  W.S.W., 
W.N.W.,  and  N.N.W. 

We  have  now  got  our  circle  divided  into  16  portions 
each  of  22^°.     The  sailor,  however,  carries  the  matter  2 


^o  THE  STORY  OF  THE  STARS. 

Steps  further,  and  by  again  subdividing  into  halves  the 
intervals  just  mentioned  he  arrives  at  the  32  "points  of 


The  points  of  the  compass. 


the  compass,"  as  they  are  called  ;  then  by  another  sub- 
division into  halves  he  obtains  64  subdivision  of  the  circle, 
though  the  final  appellation  is  not  a  "  point,"  but  a  "half- 
point." 

Speaking  generally,  the  subdivision  of  the  circle  for  the 
purpose  of  steering  a  ship  does  not  need  (except  in  special 
cases,  of  course)  any  great  refinement  ;  that  is  to  say,  an 
order  to  vary  a  ship's  course  by  half  a  point,  or  about  5^°, 
is  precise  enough  on  the  open  seas.*  But  the  astronomer 
in  measuring  angular  distances  in  the  case  of  the  sun  and 
planets,  and  still  more  in  the  case  of  the  stars,  has  to  deal 

*  This  remark  does  not  apply  to  the  larger  steamers,  whether 
ships  of  war  or  belonging  to  the  mercantile  marine.  These  when 
provided  with  steam-steering  gear  are  steered  to  single  degrees  of 
the  circle. 


BRILLIANCY  AND  DISTANCES  OF  THE  STARS.  21 

with  arcs  infinitely  smaller  than  those  which  the  "  man  at 
the  wheel  "  is  concerned  with.  Not  only  arcs  as  small  as 
\",  but  even  fractions  of  a  second  have  to  be  taken  into 
account  by  the  use  of  instruments  far  larger  in  size  and 
more  finely  graduated  than  the  portable  instruments,  such 
as  sextants  and  theodolites,  used  by  sailors  at  sea,  and  by 
surveyors  on  land. 


CHAPTER   III. 

THE   BRILLIANCY  AND   DISTANCES   OF  THE  STARS. 

The  stars  are  not  all  equally  bright,  and  custom  has 
divided  them  into  certain  classes  known  as  "  magnitudes." 
The  largest  and  brightest  are  said  to  be  stars  of  the  ist 
magnitude ;  next  come  stars  of  the  2nd  magnitude, 
and  so  on  by  a  descending  scale.  Stars  of  about  the 
6th  magnitude  are  reputed  to  be  the  smallest  visible 
to  the  naked  eye,  but  by  the  use  of  telescopes  we  can 
go  on  observing  stars  down  to  about  the  15th  magni- 
tude or  even  smaller.  It  will  be  readily  understood  that 
this  is  a  very  loose  and  arbitrary  phraseology,  but  it  has 
become  so  consecrated  by  time  and  custom  that  it  will 
certainly  never  be  set  aside.  Whilst  everybody  is  agreed 
as  to  what  is  the  brightest  star  in  the  heavens,  namely 
Sirius,  and  that  about  20  stars  are  worthy  to  be  ranked  as 
of  the  1st  magnitude,  though  less  bright  than  Sirius,  sharp 
differences  of  opinion  present  themselves  when  we  try  to 
mark  off  2nd  magnitude  stars  from  ist  magnitude  stars, 
and  still  more  when  we  have  to  define  where  the  2nd 
magnitude  stars  end  and  the  3rd  magnitude  stars  begin. 
Lower  down  in  the  scale  the  difficulties  of  classification 
become  infinitely  greater — they  may,  indeed,  be  said  to  be 
hopeless. 


2  2  THF  STORY  OF  THE  STARS. 

Considering  the  love  of  precision  and  exactness  which 
characterises  nineteenth-century  science,  it  is  somewhat 
singular  that  so  little  has  been  done  to  submit  to  meas- 
urement on  definite  principles  the  brilliancy  of  the  vari- 
ous stars,  at  any  rate  those  visible  to  the  naked  eye. 
Sir  John  Herschel  made  an  attempt  in  this  direction 
about  60  years  ago.  Many  years  afterwards  some  Ger- 
mans, especially  an  observer  named  Seidel,  nibbled  at  it, 
but  Professor  Pickering  in  America  and  the  late  Professor 
Pritchard  of  Oxford,  working  at  Oxford  and  in  Egypt,  are 
the  only  two  observers  who  have  accomplished  any  results 
worthy  of  the  subject  on  a  well-organised  basis.  Picker- 
ing's labours  at  Harvard  College  Observatory,  Boston, 
U.  S.,  have  been  published  in  the  form  of  a  catalogue  of 
4.260  stars,  whose  magnitudes  have  been  determined  in- 
strumentally  on  definite  and  intelligible  optical  principles. 
Pritchard's  catalogue  comprises  fewer  stars  than  Picker- 
ing's, but  like  its  American  rival  is  based  upon  philosophi- 
cal principles,  an  instrument  called  the  Wedge  Photometer 
having  been  employed.  Both  catalogues  labour  under  the 
disadvantage,  that  having  been  made  in  the  Northern  hemi- 
sphere they  do  not  include  the  whole  area  of  the  heavens. 

Taking  the  stars  as  we  find  them,  a  very  slight  amount 
of  attention  will  show  that  not  only  are  they  of  different 
degrees  of  brilliancy,  but  that  they  are  of  different  colours. 
More  prolonged  and  refined  study  will  disclose  the  further 
facts  that  some  of  them  vary  both  in  brilliancy  and  in 
colour.  These  matters  are  of  such  extreme  interest  that 
it  will  be  best  to  devote  a  special  chapter  to  them.  The 
brighter  stars  are  distinguished  from  one  another  in  vari- 
ous ways,  and  many  of  them  received  in  bygone  times 
quaint  and  curious  names.  At  a  ver}'  remote  period  they 
were  grouped  into  constellations,  most  of  which  survive 
to  the  present  time  and  are  recognised  to  be  of  use  to  a 
certain  extent. 


BRILLIANCY  AND  DISTANCES  OF  THE  STARS.   23", 

Leaving  the  constellations  for  treatment  in  a  separate 
chapter,  and  confining  our  attention  for  the  moment  to  the 
stars  as  individual  objects,  it  may  be  remarked  that  in 
order  to  distinguish  one  star  from  another  the  ancient 
astronomers  often  indicated  a  star  by  speaking  of  the  posi- 
tion it  occupied  in  the  constellation  to  which  it  belonged. 
Thus  Aldebaran  was  called  Ocidus  Taiiri,  "  the  Eye  of 
the  Bull."  This  custom  was  followed  and  largely  de- 
veloped by  the  Arabians,  and  many  of  the  names  invented 
by  them  are  still  in  use,  corrupted  or  transformed.  A 
German  astronomer  named  Bayer  was  the  first  to  attempt 
(about  1603)  on  any  considerable  scale  to  simplify,  and  so 
improve  the  old  plan,  but  the  Arabian  names  had,  either 
in  their  Arabian  form,  or  as  translated  into  Latin,  taken 
such  deep  root  that  many  of  them  are  even  still  in  constant 
use.  Bayer's  plan  was  to  attach  to  the  prominent  stars  of 
each  constellation  the  letters  of  the  Greek  alphabet,  though 
the  popular  idea  that  the  opening  letters  of  the  alphabet 
were  reserved  for  the  brightest  stars  and  the  later  letters  for 
the  less  conspicuous  stars,  is  unfortunately  not  universally 
true.  However  the  Greek  letters  a,  ^,  and  y,  do  indicate 
often  the  3  brightest  stars  of  a  constellation.  Bayer's 
letters  are  still  in  vogue,  the  name  of  the  constellation 
being  put  after  each  in  the  genitive  case.  Thus  the  star 
which  bears  the  name  of  Sirius  is  termed  a  Canis  Majoris. 
Arcturus  is  a  Bootis,  and  so  on.  The  Persians  are  said  to 
have  considered  3000  years  ago  that  the  whole  heavens 
were  divided  into  4  great  districts,  each  watched  over  by 
a  "  Royal  "  star.  The  4  stars,  each  very  brilliant  and 
remarkable,  which  occupied  the  important  positions  of 
"guardians  "  of  these  districts  were  Aldebaran  in  Taurus, 
Antares  in  Scorpio,  Regulus  in  Leo,  and  Fomalhaut  in 
Piscis  Australis,  but  Arago,  who  mentions  this  tradition,  can 
hardly  be  deemed  accurate  in  his  remark  that  the  4  stars 
in  question  divide  the  heavens  into  4  almost  equal  portions. 


24  THE  STORY  OF  THE  STARS. 

This  chapter  may  be  conveniently  brought  to  a  close 
with  a  list  in  the  order  of  brightness  of  the  stars  which 
are  commonly  ranked  as  of  the  ist  magnitude : — 

1.  a  Canis  Majoris  {Sirius). 

2.  a  Argus  [Canopiis).  Invisible  in  England  and  Northern 
United  States. 

3.  a  Centauri.  Invisible  in  England  and  United  States,  ex- 
cept extreme  southern  points. 

4.  a  Bootis  [Arctiirus). 

5.  )8  Orionis  {Rigel). 

6.  a  Aurigae  {Capella). 

7.  a  Lyrae  ( Vega). 

8.  o  Canis  Minoris  {Procyon). 

9.  a  Orionis  {Betelguese). 

10.  a  Eridani  (Achernar).  Invisible  in  England  and 
United  States,  except  southern  part  of  Gulf  States. 

11.  a  Tauri  {Aldebaran). 

12.  )8  Centauri.  Invisible  in  England  and  United  States, 
except  extreme  southern  points. 

13.  a  Crucis.     Invisible  in  England  and  United  States. 

14.  a  Scorpii  {Antares). 

15.  a  Aquilae  {A /fair). 

16.  o  Virginis  (Spica). 

17.  o  Piscis  Australis  {Fomnlhauf). 

18.  )8  Crucis.  Invisible  in  England  and  United  States,  ex- 
cept extreme  southern  points. 

19.  )8  Geminorum  {Pollux). 

20.  o  Leonis  {Regulus). 

21.  o  Cygni  {Deneb). 

With  respect  to  the  first  13  of  the  above  stars  it  may 
be  said  that  there  is  not  much  difference  of  opinion  as  to 
their  relative  rank  (though  some  authorities  do  make  Vega 
and  Capella  change  places),  but  as  to  the  remaining  7 
there  is  not  the  same  accord,  some  ranking  Altair  and 
Spica  before  Antares,  and  Regulus  before  Fomalhaut, 
Pollux,  and  /3  Crucis.     These  stars  are  pretty  evenly  dis- 


BRILLIANCY  AND  DISTANCES  OF  THE  STARS.  25 


tributed  between  the  Northern  and  Southern  hemispheres, 
for  10  are  Northern  and  11  Southern. 

The  following  are  the  approximate  dates  on  which 
such  of  the  foregoing  stars  as  are  visible  in  England  and 
the  United  States  come  to  the  meridian  at  midnight : — 


Procyon 

. . .  January  14 

Deneb 

..  July  31 

Pollux 

...  January  15 

Fomalhaut   . 

. .  September    3 

Regulus 

. . .  February  21 

Aldebaran    . 

. .  November  28 

Spica 

. . .  April  II 

Capella 

. .  December    8 

Arcturus 

. . .  April  24 

Rigel 

. .  December    8 

An  tares 

. . .  May  27 

Betelgueze 

. .  December  i3 

Vega 

. . .  June  29 

Sirius 

. .  December  31 

Altair 

. . .  July  18 

Not  entirely  foreign  to  the  question  of  the  brilliancy  of 
the  stars  is  the  question  of  their  distance.  At  the  first 
blush  of  the  thing  an  uninformed  reader  might  naturally 
say  that  to  measure  the  distance  of  a  star  from  the  earth 
is  impossible.  But  so  far  as  the  principle  of  this  task  is 
concerned  the  problem  is  an  easy  one.  It  is  in  the  prac- 
tical working  out  of  the  principle  that  the  difficulty  lies ; 
and  this  again  rather  arises  from  the  extreme  delicacy  of 
the  measurements  and  necessary  safeguards  than  from 
any  other  cause.  The  process  merely  involves  the  taking 
of  certain  angular  measurements  and  applying  to  them 
certain  familiar  theorems  of  trigonometry.  It  differs 
scarcely  at  all  from  analogous  operations  which  are  car- 
ried out  every  day  on  the  earth  by  those  engaged  in  land 
surveying.  What  is  involved  will  perhaps  be  understood 
by  considering  what  happens  when  a  person  enters  a  large 
park  at  one  end,  intending  to  cross  to  the  far  side  where 
there  are  a  number  of  trees  in  an  avenue,  passing  <?«  route 
2  or  3  trees  in  the  open.  The  trees  in  the  far-off  avenue 
seem  to  be  at  no  great  distance  apart,  and  the  trunk  of 
one  of  them  is  nearly  hidden  by  the  trunk  of  one  in  the 


2  6  THE  STORY  OF  THE  STARS. 

middle  of  the  park ;  but  soon  after  the  pedestrian  has 
started  (perhaps  when  he  has  got  over  50  yards)  he  notices 
that  the  2  last-named  trees,  which  a  minute  or  two  ago 
seemed  almost  in  contact,  are  evidently  some  distance 
apart,  and  after  walking  for  perhaps  another  minute  (say 
another  50  yards)  he  sees  cause  to  infer  that  a  space  of 
perhaps  120  yards  separates  the  trees  which,  before  he  got 
in  motion,  appeared  almost  to  touch.  This  transforma- 
tion is  the  effect  of  "  parallax,"  and  the  apparent  displace- 
ment of  the  trees  is  due  to  the  real  displacement  of  the 
observer,  owing  to  his  having  used  his  legs.  But  suppos- 
ing the  2  trees  singled  out  as  above,  instead  of  being 
within  the  same  park  close  at  hand  had  been  2  miles  off, 
an  advance  of  50  yards  would  have  caused  so  trifling  a 
displacement  that,  though  a  telescope  provided  with  a  mi- 
crometer would  have  detected  it,  the  naked  eye  might  not 
have  done  so.  Why  this  ?  Because  in  the  first  case  the 
distance  traversed  (50  yards)  was  a  large  fraction  of  the 
distance  (say  400  yards)  at  which  the  trees  were  situated 
from  the  starting-point  (as  50  :  400  :  :  i  :  8).  But  in  the 
second  supposed  case  the  distance  traversed  (50  yards) 
was  but  a  small  fraction  of  the  whole  distance  (say  4000 
yards)  separating  the  pedestrian  from  the  trees.  The 
proportion  is  now  to  be  expressed  thus : — As  50  :  4000  :  : 
I  :  80. 

Let  us  apply  these  similes  to  the  stars.  An  observer 
on  January  ist  is  using  his  telescope  when  the  earth  is  at 
a  certain  known  point  in  its  annual  orbit  round  the  sun. 
He  determines  the  position  of  a  certain  star.  He  waits  6 
months,  and  then,  on  July  ist,  again  determines  the  place 
of  his  selected  star ;  he  finds  it  occupies  the  same  place. 
He  is  on  July  ist  removed  by  twice  the  radius  of  the 
earth's  orbit,  or  186  millions  of  miles,  from  the  place  he 
occupied  on  January  ist.  If,  notwithstanding  this  enor- 
mous displacement  of  himself,  the  star  seems  to  have  un- 


BRILLIANCY  AND  DISTANCES  OF  THE  STARS.     27 

dergone  no  displacement,  our  observer  argues  that  the 
star  must  be  so  far  off  that  186  millions  of  miles  is  a  frac- 
tional part  of  its  distance,  too  small  to  be  appreciable,  just 
as  the  50  yards  mentioned  above  is  only  a  small  fractional 
part  of  4000  yards. 

The  principle  of  all  this  has  been  applied  to  several 
hundred  stars,  but  only  about  2  dozen  have  yielded  posi- 
tive results.  These  results,  so  far  as  they  go.  seem  to  tell 
us  that  the  nearest  star  of  those  experimented  upon  is 
a  Centauri,  and  that  the  4  next  nearest  are  61  Cygni,  21 185 
Lalande  Ursse  Majoris,  Sirius,  and  fi  Cassiopeise. 

Such  standards  as  miles,  or  even  millions  of  miles,  are 
quite  unmanageable  in  dealing  with  distances  such  as 
those  which  separate  the  nearest  stars  from  the  earth,  so 
it  is  customary  to  employ  as  the  unit  of  stellar  distances 
the  distance  traversed  by  light  in  one  year.  Now  light 
travels  at  the  rate  of  about  185,000  miles  in  one  second,  or 
about  63,000  times  the  earth's  distance  from  the  sun  in 
one  year.  Applying  these  figures  to  the  circumstances  of 
a  Centauri,  we  find  that  as  the  parallax  of  that  star  is  only 
about  f  of  a  second  of  arc,  a  ray  of  light  from  it  would  not 
reach  the  earth  in  less  than  4I  years.  This  distance  ex- 
pressed in  miles  amounts  to  24,750,000,000,000  ;  and  a  Cen- 
tauri is,  so  far  as  is  known,  t/^e  nearest  star  !  The  reader 
will  hardly  require  any  further  explanation  of  the  state- 
ment made  above  that  a  mile  is  a  hopelessly  ineffective 
and  inadequate  unit  in  which  to  express  stellar  distances. 
It  only  remains  to  add  that  it  is  doubtful  whether  any  of 
the  stellar  parallaxes  hitherto  arrived  at  are  accurate  to 
within  -jV  of  a  second  of  arc.  Now  -^-^  of  a  second  is 
the  angle  subtended  by  ^\  of  an  inch  at  a  distance  of  10 
miles !  Observations  of  stellar  parallax,  therefore,  need 
very  first-class  instruments  and  men,  and  it  is  on  this  ac- 
count that  the  results  up  to  the  present  time  are  neither 
very  numerous  nor  particularly  consistent. 


28  THE  STORY  OF  THE  STARS. 


CHAPTER    IV. 

THE  GROUPING   OF  THE   STARS    INTO    CONSTEL- 
LATIONS. 

The  visible  stars  are  commonly  treated  as  arranged  in 
groups  which  are  called  "  constellations."  The  circum- 
stances under  which  this  grouping  was  brought  about  in- 
volve so  many  interesting  historical  points  that  the  history 
of  the  constellations  may  well  form  a  separate  chapter. 
Let  me  then  limit  the  present  chapter  to  a  few  general  hints 
and  remarks  on  the  finding  of  the  constellations. 

A  reader  who  wishes  to  be  able  to  do  this  with  facility 
must  enter  upon  the  study  of  the  stars  methodically,  and 
in  accordance  with  a  definite  plan,  and  must  be  prepared 
to  persevere  with  his  work  at  regular  and  not  very  long 
intervals  of  time  through  an  entire  period  of  12  months. 
In  making  this  suggestion  I  lay  a  good  deal  of  stress  on 
the  work  being  done  systematically,  and  without  any  con- 
siderable gaps  of  time  in  the  doing  of  it.  The  importance 
of  this  will  be  understood  when  it  is  borne  in  mind  that  a 
given  star  comes  to  the  meridian  every  night  4  minutes 
sooner  than  it  did  on  the  preceding  night.  This  has  the 
effect  in  the  course  of  a  fortnight  of  displacing  a  star  by 
1 5°  of  arc,  the  time  of  observation  remaining  the  same.  In 
other  words,  if  an  observer  wishes  to  see  a  given  star  on 
the  meridian  a  fortnight  after  his  first  observation  of  it, 
he  must  take  post  at  his  telescope  (supposing  he  is  using 
one  which  only  works  up  and  down  in  the  meridian)  one 
hour  earlier  in  the  evening  than  the  hour  at  which  the  first 
observation  was  made.  It  would  soon  be  seen  in  practice 
why  there  was  not  only  no  advantage  in  thus  altering 
one's  times  but  a  positive  disadvantage.  The  ordinary 
object  of  a  professed  student  would  be,  not  to  have  a  con- 
stant change  in  the  hours  of  his  occupation,  but  to  have 


GROUPING  OF  STARS  INTO  CONSTELLATIONS.  29 

a  constant  change  in  the  occupation  itself ;  that  is,  in  the 
stars  he  is  wishing  to  learn  the  names  of,  the  hours  of 
work  remaining  (for  his  personal  convenience)  probably 
much  the  same,  say  9  p.  m.  to  midnight. 

There  is  another  and  also  cogent  reason  for  keeping  at 
this  work  regularly  and  avoiding  long  breaks.  Though 
the  stars  maintain,  so  far  as  they  themselves  are  con- 
cerned, speaking  generally,  the  same  relative  positions 
throughout  the  year,  yet  it  makes  a  good  deal  of  differ- 
ence to  the  unpractised  eye  in  the  identification  of  par- 
ticular stars  whether  they  are  looked  at  whilst  they  are  in 
the  neutral  position  (as  it  may  be  called)  of  the  meridian, 
or  when  they  are  oblique  to  the  meridian,  eastwards  of  it 
and  rising,  or  westwards  of  it  and  setting.  These  differ- 
ences can  only  be  properly  appreciated  by  being  consid- 
ered experimentally  on  a  starlight  night  in  the  open  air, 
for  no  verbal  account  of  them  can  be  adequate. 

A  tourist  who  is  travelling  through  a  hilly  country,  un- 
less he  is  a  professional  land  surveyor  employed  on  profes- 
sional work,  does  not  go  through  the  formality  of  marking 
off  his  meridian  line  and  of  setting  out  by  an  instrument 
the  bearings  of  particular  peaks  and  towers  for  the  pur- 
pose of  getting  a  record  of  them  on  paper.  As  a  mere 
traveller  for  pleasure  he  will  probably  have  with  him  noth- 
ing more  than  a  map  and  a  pocket  compass  ;  and  his  aim 
will  be  only  to  identify  particular  mountain-tops,  church 
towers,  villages,  or  other  objects  of  special  interest. 
There  is  only  one  way  in  which  he  will  attempt  to  pro- 
ceed. Assuring  himself  by  means  of  his  guide-book  or 
map,  or  by  the  aid  of  local  information,  of  some  one,  two 
or  three  prominent  objects,  the  identity  of  which  evidently 
admits  of  no  doubt,  he  will  then  feel  his  way  by  eye  first 
from  one  point  and  then  from  another  point,  constantly 
consulting  his  map  and  compass.  By  some  such  process 
as  this,  after  starting  with  two  or  three  objects  recognised 


30 


THE  STORY  OF  THE  STARS. 


to  a  certainty,  he  will  be  able  to  learn  the  names  of  all  the 
places  within  sight  which  he  wishes  to  identify,  to  the 
number  it  may  be  of  several  dozen. 

This  mode  of  procedure  may  be  commended  to  the 
would-be  student  of  the  Starry  Heavens.  Such  an  one 
should  obtain  practice  for  his  work  by  making  sure  at 
starting  of  the  names  of  two  or  three  prominent  stars. 
He  should  then  feel  his  way  in  between  them  by  fixing  in 
his  mind,  one  after  another,  minor  triangles  of  stars,  com- 
paring every  one  with  his  map  as  he  goes  along,  taking 
particular  care  not  to  proceed  with  the  identification  of  a 
second  triangle  until  he  has  quite  satisfied  himself  that  he 
has  accurately  identified  the  stars  forming  the  first. 

It  has  already  been  mentioned  that  the  practice  has 
long  prevailed  of  designating  the  more  conspicuous  stars 
in  every  constellation  by  the  letters  of  the  Greek  alphabet. 
An  adequate  knowledge  of  the  small  letters  of  this  alpha- 
bet is  therefore  an  indispensable  accomplishment  for  every 
student  of  the  starry  heavens.     These  letters  are  : — 


a 

Alpha. 

fi 

Beta. 

y 

Gamma. 

5 

Delta. 

6 

Epsilon. 

c 

Zeta. 

V 

Eta. 

e 

Theta. 

I 

Iota. 

K 

Kappa. 

\ 

Lambda. 

M 

Mu. 

V 

Nu. 

1 

Xi. 

0 

O-mlcron 

w 

Pi. 

p 

Rho. 

<r 

Sigma. 

T 

Tau. 

V 

Upsilon. 

<P 

Phi. 

X 

Chi. 

^ 

Psi. 

0) 

Omega. 

I  will  now  endeavour  to  apply  the  foregoing  ideas  to  the 
study  of  the  stars,  starting  with  the  Great  Bear  as  being 
the  most  conspicuous  of  those  constellations  which  never 


GROUPING  OF  STARS  INTO  CONSTELLATIONS.  3 1 

set  in  the  latitude  of  London.  The  tail  and  hind-quarters 
consist  of  7  brilliant  stars.  Four  of  these  (a,  /3,  7,  S)  have 
long  been  likened  to  a  wain  or  waggon,  the  other  3  (e,  ^,  rj) 
being  fancifully  called  the  horses  ;  the  7  taken  together 
making  "  Charles's  Wain  "  or  the  "  Plough  " — to  mention 
some  old  English  designations.*  The  hind  wheels  or  the 
2  stars  (/3,  a)  farthest  from  the  horses  are  called  the 
"  Pointers,"  because  they  point  towards  the  Pole  Star  (a 
Ursse  Minoris)  at  the  tip  of  the  Little  Bear's  tail.  A  line 
carried  from  the  Pointers  beyond  the  Pole  Star  leads  to 
Cepheus  and  Cassiopeia — constellations  abutting  on  the 
Milky  Way  where  it  comes  nearest  to  the  Pole.     Cassio- 


FiG.  3.— Ursa  Major  and  Polaris. 

peia  comprises  several  prominent  stars  which  f 
resembling  the  letter  W  or  the  letter  M,  accoroi 

*  The  popular  name  in  the  United  States  is  the  "  " ' 
of  the  seven  stars  are  not  visible  at  their  lowp^ '■•  •~-'       '->    sotit 
of  about  the  latitude  of  T^hilade^nhii.  but  th-^  t'"  s"  nevei 

set  at  any  place  north  of  Ch-w    "ton.  "^    C. 


32         THE  STORY  OF  THE  STARS. 

time  of  year  at  which  they  are  viewed.  The  2  northern- 
most wheels  of  the  waggon  {8,  a,  Ursas  Majoris)  point  to 
the  bright  star  Capella  in  Auriga,  which  is  also  circum- 
polar  in  British  latitudes,  but  not  in  the  United  States. 
The  stars  of  the  Great  Bear  may  be  advantageously  em- 
ployed by  the  student  as  an  approximate  scale  of  angular 
distances  in  making  estimates  of  the  distances  between 
star  and  star.  Thus  : — The  Pointer  (a)  nearest  to  the 
Pole  is  281°  from  it  ;  from  /3  to  y  is  8° ,  from  ^  to  77  is  7°  ; 
from  S  to  e  is  $^°  ;  from  a  to  /3  is  5°  ;  from  y  to  8  and  from 
f  to  ^  is  in  both  cases  4^°. 

Descending  diagonally  along  the  Milky  Way  from  Cas- 
siopeia towards  Capella  (a  Aurigas)  we  come  to  a  Persei, 
and  a  little  farther  from  the  Pole  we  find  Algol  O  Persei), 
a  celebrated  variable  star  in  Medusa's  head.  If  we  carry 
our  eyes  across  the  Milky  Way  in  the  opposite  direction 
we  arrive  at  Deneb,  the  brightest  star  (a)  of  Cygnus  (the 
Swan) ;  and  beyond  Cygnus,  a  little  out  of  the  Milky 
Way,  is  Vega,  the  brightest  star  (a)  in  Lyra  (the  Lyre). 
Draco  (the  Dragon)  consists  of  a  long  winding  chain  of 
stars  running  partly  round  Ursa  Minor  (the  Little  Bear). 
In  the  space  bounded  by  Cassiopeia,  Cygnus,  and  Draco," 
lies'the  constellation  Cepheus.  j 

Near  Algenib  (y  Pegasi)  and  pointing  directly  towards  ' 
it  are  2  conspicuous  stars  of  Andromeda  (a,  /3),  whilst  a 
3rd  (y)  lies  a  little  beyond  them.  Andromeda  will  always 
be  readily  known  by  reason  of  the  connection  of  the  bright 
star  (a)  in  her  head  with  the  large  trapezium  of  Pegasus 
(a,  /3,  y),  the  4  stars  forming  the  well-known  "  Square  of 
Pegasus." 

An  imaginary  line  projected  through  the  Great  Bear 
and  Capella  passes  to  the  "  Pleiades,"  the  celebrated  group 
in  Taurus  (the  Bull),  of  which  we  shall  have  more  to  say 
hereafter  (in  Chap.  XIV. posif), Sind  then  turning  at  aright 
angle  reaches  Aldebaran  (a  Tauri,  a/t'as  the  "Bull's-eye  ") 


GROUPING  OF  STARS  INTO  CONSTELLATIONS.  ^3 

and  the  shoulders  (a,  y)  of  Orion.  Orion  is  to  the  naked 
eye  by  far  the  most  magnificent  of  all  the  constellations, 
whilst  it  is  peculiarly  rich  in  telescopic  objects.  Orion 
may  always  be  identified  by  the  3  bright  stars  in  its 
"  Belt,"  which  occupies  the  middle  of  a  large  quadrangle 
of  still  brighter  stars.  Aldebaran  is  a  reddish  star,  the 
most  prominent  of  the  "  Hyades,"  a  cluster  resembling  the 
letter  V,  and  not  far  from  the  Pleiades.  Aldebaran,  the 
Pleiades,  and  Algol  (/3  Persei)  make  the  upper,  while  Men- 
kab  (a  Ceti),  in  the  Whale's  jaw,  with  Aries,  make  the 
lower  points  of  a  large  W.  The  head  of  Aries  (the  Ram) 
is  indicated  by  two  principal  stars  (a,  /3),  the  latter  of 
which  has  a  small  attendant. 

An  imaginary  line  drawn  from  the  Fole  Star  and  car- 
ried midway  between  the  Great  Bear  and  Capella  (a 
Aurigae)  passes  to  Castor  and  Pollux  (a,  ^  Geminorum), 
two  well-known  stars  in  the  heads  of  Gemini  the  Twins ; 
whilst  forwards  to  the  S.  of  Gemini  it  will  meet  Procyon 
(a  Canis  Minoris)  the  brightest  star  of  the  Lesser  Dog. 
From  thence  by  bending  the  hne  across  the  Milky  Way 
and  carrying  it  as  far  again  it  will  reach  Sinus  (a  Canis 
Majoris)  in  the  Greater  Dog's  mouth,  and  will  then  pass 
to  a  somewhat  conspicuous  star,  which  in  England  is  quite 
in  the  southern  horizon,  a  Columbas,  33°  S.  of  the  middle 
star  in  Orion's  belt. 

Algol  (j8  Persei)  and  Castor  point  to  Regulus  (a  Leonis, 
alias  Cor  Leonis,  the  "  Lion's  heart ")  which  is  situated  at 
one  end  of  an  arc  with  Denebola  (/3  Leonis),  the  tuft  of 
the  Lion's  tail  at  the  other  end.  S.  of  Regulus  and  pre- 
ceding it,  /.  e.,  coming  to  the  meridian  before  it  by  about 
f  hour,  is  Cor  Hydras  (a),  the  space  between  them  being 
occupied  by  the  modern  and  insignificant  constellation  of 
the  Sextant. 

The  Pole  Star  and  the  middle  horse  of  the  waggon  (O 
direct  us  to  Spica,  the  brightest  star  (a)  of  Virgo,  consid- 
3 


34         THE  STORY  OF  THE  STARS. 

erably  distant,  whilst  forwards,  towards  tlie  horizon,  we 
shall  reach  Centaurus.  The  Pole  Star  and  the  first  horse 
(rf  Ursas  Majoris)  conduct  us  nearly  upon  Arcturus  in 
Bootes  (a),  by  which  fine  star,  with  Spica  (a  Virginis)  and 
Regulus  (a  Leonis),  a  splendid  triangle  is  formed.  Fol- 
lowing at  a  distg.nce  to  the  southward  is  Antares  (a 
Scorpii),  *'  the  Rival  of  Mars,"  which  with  Arcturus  and 
Spica  constitute  another  large  triangle,  having  within  it 
the  two  bright  stars,  a  and  ^3  Librae. 

Corona  Borealis,  the  Northern  Crown,  is  nearly  in  a 
line  between  Vega  (a  Lyras)  and  Arcturus  (a  Bootis)  ;  and 
the  heads  of  Hercules  and  Ophiuchus  lie  between  Lyra 
and  Scorpio.  In  the  Milky  Way,  below  the  part  nearest 
to  Lyra  and  on  a  line  drawn  from  Arcturus  through  the 
head  of  Hercules,  is  the  bright  star  Altair  in  the  Eagle  (a 
Aquilae),  which  makes  with  Vega  and  Deneb  (a  Cygni)  a 
conspicuous  triangle.  Closely  following  Aquila  is  a  re- 
markable group  of  stars  forming  the  constellation  Del- 
phinus,  the  Dolphin. 

The  last  and  brightest  (a)  of  the  3  principal  stars  in 
Andromeda  makes  with  3  stars  of  Pegasus  (a,  /3,  y)  the 
large  "  Square  "  or  trapezium  already  mentioned,  of  which 
the  side  formed  by  /3  and  a  points  to  Fomalhaut  (a  Piscis 
Australis).  situated  in  the  mouth  of  the  Southern  Fish, 
between  the  tails  of  Cetus  and  Capricornus. 

The  line  of  the  ecliptic  may  without  difficulty  be  traced 
by  the  observer  when  his  eye  becomes  familiar  with  the 
stars  now  about  to  be  enumerated.  Not  far  from  the 
Pleiades  are  the  Hyades  with  Aldebaran  (a  Tauri),  a  little 
S.  of  the  ecliptic.  To  the  N.  W.  of  Aldebaran  at  some 
distance  is  the  chief  star  of  Aries  (a);  wnile  to  the  N.  E. 
of  that  star  are  Castor  and  Pollux  (a  and  fi  Geminorum). 
Regulus  (a  Leonis)  is  on  the  line  of  the  ecliptic;  an 
Spica  (a  Virginis)  is  but  a  ver\-  l-'t-  '  p  S.  of  it. 

start  being  thus  made  with  the  •  .  odiacal  con- 


GROUPING  OF  STARS  INTO  CONSTELLATIONS.  35 

stellations  will  be  easily  distinguished  in  their  order  fron> 
W.  to  E.  as  follows : — Aries  lies  immediately  between; 
Andromeda  on  the  N.  and  Cetus  on  the  S.,  the  three 
asterisms  reaching  nearly  from  the  horizon  to  the  zenith  ;. 
Taurus  will  be  recognised  by  the  Pleiades,  Aldebaran  (a) 
and  the  Hyades  ;  Gemini,  the  highest  of  the  signs  as  seen 
in  the  Northern  hemisphere,  by  Castor  and  Pollux  (a  and 
/3) ;  Cancer,  by  the  historic  group  Prassepe,  in  the  midst 
of  a  waste  rather  void  of  stars  ;  Leo  by  the  stars  Regulus. 
(a)  and  Denebola  (/3)  ;  Virgo,  by  Spica  (a)  to  the  S.  of 
Coma  Berenices;  Libra  in  mid-distance  between  Virgo- 
and  the  next  constellation  Scorpio  ;  Scorpio,  by  the  red 
star  Antares  (a)  and  its  3  other  very  conspicuous  stars  (/3^ 
8,  TT,) ;  Sagittarius  as  being  the  lowest  (/.  e.,  most  south- 
erly) of  all  the  signs  ;  Capricornus  S.  of  the  Dolphin  ; 
Aquarius  under  the  neck  of  Pegasus ;  and  the  Pisces  be- 
tween Pegasus,  Andromeda,  and  Cetus.  The  following 
familiar  lines,  though  they  do  not  rise  to  a  high  standard 
of  "  poetry,"  are  nevertheless  very  convenient  as  an  aid  to- 
the  memory : — 

The  J?am,  the  Bu//,  the  heavenly  Twins, 
And  next  the  Crab,  the  Lion,  shines. 

The  Virgin,  and  the  Scales ; 
The  Scorpion,  Archer,  and  Sea-goat, 
The  Man  that  holds  the  water-pot. 

And  Fish  with  glitt'ring  tails. 

The  account  just  completed  of  what  may  be  called  a. 
"  personally  conducted  "  tour  of  the  heavens,  is  at  the  best 
a  hasty  and  superficial  performance,  and  I  hope  that  the 
bulk  of  my  readers  who  have  accompanied  me  thus  far 
will  aspire  to  something  higher  and  more  exact,  even 
though  there  may  be  involved  some  details,  the  mastery 
of  which  will  require  a  certain  amount  of  effort  and  appli- 
cation. 


;^6  THE  STORY  OF  THE  STARS. 

A  full  list  of  the  several  constellations  arranged  in  the 
order  in  which  they  come  to  the  meridian,  that  is  to  say 
in  the  order  of  their  Right  Ascensions,  will  be  found  in 
the  Appendix  ;  but  it  is  necessary  to  explain  here  what 
the  term  "  Right  Ascension  "  means,  and  also  what  an- 
other and  allied  term  "  Declination  "  means.  Perhaps  this 
will  be  easiest  done  by  means  of  a  terrestrial  analogy. 

Everybody,  I  suppose,  knows  that  Khartoum,  the 
scene  of  a  grievous  tragedy,  is  in  Africa.  But  how  many 
of  my  readers  could  open  an  atlas,  turn  to  the  map  of 
Africa,  and  go  straight  with  his  finger-tip  to  the  city  of 
Khartoum  ?  But  if  he  knew  beforehand  that  Khartoum 
•was  situated  in  latitude  15°  35'  N.  and  longitude  32°  30' 
E.  of  Greenwich,  the  finding  of  it  would  be  an  easy  mat- 
ter, promptly  accomplished  by  the  aid  of  a  network  of 
lines  running  up  and  down  and  across  the  face  of  the 
map.  Now  what  latitude  and  longitude  are  for  terrestrial 
geography,  declination  and  right  ascension  are  for  celestial 
geography  (so  to  speak),  only  just  a  little  different. 

It  is  not  difficult  to  make  clear  what  declination  is,  but 
an  explanation  of  right  ascension  will  not  be  taken  in  so 
readily.  We  have  already  seen  that  the  whole  visible  sky 
is  to  be  regarded  as  in  some  sense  a  sphere,  with  us,  on 
the  earth,  apparently  as  its  centre  ;  and  that  the  aforesaid 
sphere  turns  on  an  imaginary  axis  directed  to  2  poles. 
Midway  between  the  2  poles  lies  the  equator,  and  as  it  is 
a  semi-circle  (or  180°)  from  pole  to  pole  the  polar  distance 
of  the  celestial  equator  (which  is  the  earth's  equator  pro- 
longed to  the  heavens)  will  be  90°.  For  some  purposes 
it  is  occasionally  the  practice  of  astronomers  to  count 
angular  distances  from  the  N.  pole  towards  the  equator, 
but  the  regular  and  ordinary  practice  is  to  count  from  the 
•equator  to  the  poles,  N.  or  S.,  as  the  case  may  be.  Hence 
we  obtain  the  expressions  "  north  declination  "  and  "  south 
declination,"  as  applied  to  the  places  of  the  stars,  and 


GROUPING  OF  STARS  INTO  CONSTELLATIONS.  37 

these  expressions  are,  in  a  certain  sense,  the  counterpart 
of  the  expressions  "  north  latitude  "  and  "  south  latitude  " 
used  with  reference  to  j>laces  on  the  earth. 

The  term  "  right  ascension  "  is  not  to  be  brought  home 
to  the  mind  quite  so  easily.  In  the  case  of  terrestrial 
longitudes  there  is  no  difficulty  in  finding  a  definite  and 
immovable  terminus  to  start  from.  Many  European  na- 
tions are  using  the  meridian  of  Greenwich  for  this  pur- 
pose, though  Frenchmen  count  from  Paris,  Germans  from 
Berlin,  and  so  on.  But  in  the  case  of  the  stars  a  fixed 
zero  is  not  so  easy  to  find  and  still  less  easy  to  keep.  How- 
ever, astronomers  have  long  been  agreed  to  make  what  is 
called  the  "  First  point  of  Aries,"  alias  the  "  Vernal 
Equinox,"  their  starting-point  for  right  ascensions.  This 
is  the  point  where  the  sun,  in  the  course  of  its  annual 
journey  through  the  signs  of  the  zodiac,  crosses  the  equa- 
tor, going  from  south  to  north,  in  the  month  of  March  on 
the  20th  day  of  that  month.  The  phrase  "  vernal  equi- 
nox "  means  the  moment  of  equal  day  and  equal  night  in 
the  spring.*  It  is  also  at  this  moment  that  the  clocks 
used  by  astronomers  in  their  observatories  read  oh.  om. 
OS.  Owing  to  the  operation  of  disturbing  causes,  the  na- 
ture and  description  of  which  do  not  belong  to  this  chap- ' 
ter,  or  indeed  to  this  volume,  this  point  is  incessantly 
shifting  in  the  heavens.  By  virtue  of  a  change  called 
"the  precession  of  the  equinoxes,"  the  actual  place  of  the 
equinox  goes  backwards  about  50"  every  year,  and  this  is 
what  I  meant  by  saying  above  that  the  zero  for  celestial 
longitudes  is  not  only  not  easy  to  find  but  when  found 
cannot  readily  be  kept.  It  must  suffice,  then,  for  my 
present  purpose  to  remark  that  if  we  wish  to  fix  the  right 
ascension  of  a  star  we  must  imagine  a  meridian  to  pass 
through  it ;  then  imagine  a  meridian  to  pass  through  the 

*  Lat.  ver^  spring ;  cequus^  equal ;  nox^  night. 


38         THE  STORY  OF  THE  STARS. 

vernal  equinox  and  note  the  angle  which  the  former 
Tneridian  makes  with  the  latter  measured  in  degrees  of 
arc  along  the  equator  from  W.  to  E.  That  angle  will  be 
the  star's  R.  A.  It  may  be  expressed  either  in  degrees, 
minutes,  and  seconds  of  arc  (°  ' ").  o^  iri  hours,  minutes, 
and  seconds  of  time  (h.  m.  s.).  The  latter  method  is  now 
universally  employed,  the  former  having  been  discarded. 

The  relation  of  arc  to  time  in  connection  with  the 
measurement  of  angles  of  right  ascension  will  be  readily 
remembered  by  noting  that  a  minute  or  second  of  time 
represents  a  space  of  1 5  times  the  corresponding  denomi- 
nation in  arc,  while  the  hour  is  1 5  times  one  degree,  that 
is  15°.  The  minute  and  second  of  time  are  denoted  by 
the  initial  letter  of  their  names,  whilst  the  minute  and 
second  of  arc  are  denoted  by  special  symbols.  Thus  we 
arrive  at  the  following  little  table  which  the  reader  should 
get  clearly  fixed  on  his  mind  : — 


I**  =  15 
i«n  =  15' 
18  --  15' 


I     =  4°' 

I'    =  4^ 
i"    =  o.o66» 


Perhaps  this  is  as  good  a  place  as  any  at  which  to 
warn  the  reader  against  a  trap  which  he  is  very  apt  to  fall 
into.  The  "  signs  of  the  zodiac  "  are  not  the  same  as  the 
"  constellations  of  the  zodiac  "  (more  often  spoken  of  as 
the  zodiacal  constellations).  Twenty  centuries  or  so  ago 
the  astronomers  of  antiquity,  with  the  12  zodiacal  constel- 
lations within  their  knowledge,  got  into  the  natural  and 
not  inconvenient  habit  of  talking  of  the  sun  in  its  apparent 
annual  journey  through  the  heavens  along  the  ecliptic  as 
passing  successively  into  and  out  of  the  several  signs  of 
the  zodiac.  Each  of  these  signs  was  regarded  as  occu- 
pied by  a  constellation  from  which  it  took  its  particular 
name.  Commencing  at  the  vernal  equinox  the  first  30° 
through  which  the  sun  passed,  or  the  region  of  stars  in 


THE  HISTORY  OF  THE  CONSTELLATIONS.       39 

which  the  sun  was  located  during  the  month  following, 
was  called  the  sign  Aries.  The  second  30°  was  called 
the  sign  Taurus,  and  so  on  through  the  12  signs,  which 
are  identical  in  name  and  follow  in  the  same  order  as  the 
existing  12  zodiacal  constellations.  Although  there  are 
still  12  signs  and  12  constellations,  sign  and  constellation 
no  longer  correspond.  Though  the  sun  when  it  crosses 
the  equator  in  the  month  of  March  enters  the  sig7i  Aries, 
it  does  not  reach  the  constellation  Aries  till  nearly  a  month 
later.  This  discrepancy  is  due  to  the  yearly  accumulations 
of  50"  each  which  have  been  going  on  during  the  20  cen- 
turies mentioned  and  which  are  connected  with  the  phe- 
nomenon of  the  precession  of  the  equinoxes  already  briefly 
alluded  to. 

These  preliminary  explanations  will  suffice  to  enable 
the  reader  now  to  settle  down  seriously  to  a  study  of  the 
constellations.  This  task  must  be  carried  out  on  starlight 
nights  with  the  aid  of  a  good  star-atlas  *  and  a  bull's-eye 
lantern,  assisted  or  not,  as  may  be  convenient,  by  an 
opera-glass.  In  the  Appendix  will  be  found  a  Table  of 
the  constellations,  omitting  a  few  insignificant  modern 
ones  not  generally  recognised  by  astronomers. 


CHAPTER   V. 

THE  HISTORY   OF   THE   CONSTELLATIONS. 

To  the  grouping  of  the  stars  into  constellations  may 
well  be  applied  the  legal  phrase  that  the  custom  is  so  an- 
cient that  the  memory  of  man  runneth  not  to  the  contrary. 

*  I  have  found  no  English  one  as  good  as  Keith  Johnston's,  edited 
by  Hind  :  and  this  because  the  stars  show  as  white  on  a  deep  blue 
background.  Klein's,  published  by  S.  P.  C.  K.,  is  also  cheap  and 
very  good. 


40         THE  STORY  OF  THE  STARS. 

The  germs  of  it  are  evidently  to  be  found  in  Holy  Scrip- 
ture. The  three  following  passages,  which  I  cite  from  the 
Revised  Version,  whatever  else  may  be  said  of  them, 
clearly  imply  that  the  allusions  are  to  some  well-estabhshed 
usage : — 

"  Which  maketh  the  Bear,  Orion,  and  the  Pleiades,  and  the 
chambers  of  the  south.'"      (Job  ix.  g.) 

*'  Canst  thou  bind  the  cluster  of  the  Pleiades, 
or  loose  the  bands  of  Orion  ?     Canst  thou  lead 
forth  the  Mazzaroth  in  their  season  ?     Or 
canst  thou  guide  the  Bear  with  her  train  ?" 

(Job  xxxviii.  31-2.) 

"  Seek  Him  that  maketh  the  Pleiades  *  and  Orion." 

(Amos  V.  8.) 

The  constellations  now  in  use  are  about  80  or  90  in 
number,  counting  a  few  minor  ones  devised  during  the  last 
century,  chiefly  for  the  Southern  hemisphere,  but  by  no 
means  counting  all  that  have  been  proposed.  It  has  been 
well  remarked  : — "  Half  a  century  ago  no  astronomer 
seemed  comfortable  in  his  position  till  he  had  ornamented 
some  little  cluster  of  stars  of  his  own  picking  with  a  name 
of  his  own  making."  Of  the  constellations  now  recog- 
nised, no  fewer  than  48,  and  those  including  with  scarcely 
any  exception  the  largest  and  best  known,  are  recorded 
by  Ptolemy,  and  therefore  have  an  unchallenged  antiquity 
of  2000  years,  yet  the  date  of  the  actual  invention  of  even 
one  of  them  is  quite  unknown.  Seneca  attributed  the 
subdivision  of  the  heavens  into  constellations  to  the  Greeks 
1400  years  before  Christ,  but  there  is  no  proof  of  this,  and 
if  it  is  permissible  to  draw  inferences  without  having  many 
facts  to  go  upon  (a  common  practice  nowadays),  I  should 
be  rather  inclined  to  give  some  of  the  credit  of  inventing 

*  The  Authorized  Version  has  here  "The  Seven  Stars." 


THE  HISTORY  OF  THE  CONSTELLATIONS.       41 

the  constellations  to  the  Chaldaeans  or  Egyptians,  or  to 
both  of  them  in  shares,  the  Egyptians  having  developed 
that  which  they  derived  from  the  Chaldasans,  as  the  Chal- 
dseans  may  have  developed  something  they  derived  from 
peoples  which  preceded  them.  Some  writers,  indeed, 
have  thought  that  a  much  greater  antiquity  should  be  as- 
signed to  the  constellations,  and  there  are  not  wanting 
traces  of  proof  to  support  this  idea.  Neglecting  for  the 
moment  the  ancient  constellations  as  a  whole,  it  certainly 
seems  clear  that  a  special  degree  of  antiquity  attaches  to 
the  signs  of  the  zodiac,  and  no  wonder,  seeing  that  they 
remind  us,  amongst  other  things,  of  the  apparent  annual 
path  of  the  sun  amongst  the  stars. 

It  seems  more  than  probable — almost  certain — that 
the  word  "  Mazzaroth  "  quoted  above  from  Job  xxxviii.  32, 
and  left  untranslated  in  the  text  by  the  authors  of  the  Re- 
vised Version,  means  what  they  have  suggested  in  the 
margin,  namely,  the  circle  of  the  zodiac.  And  it  is  quite 
consistent  with  this  to  find,  as  a  modern  writer  has  pointed 
out,  that : — "  These  signs  were  known  among  all  nations 
and  in  all  ages.  From  the  almost  antediluvian  chronol- 
ogies of  China,  India,  and  Egypt,  to  the  traditions  of  the 
recently  discovered  islands  of  the  South  Sea,  traces  of 
them  are  discovered  most  clearly  among  the  most  ancient 
and  earliest  civilised  nations.  In  the  remains  of  Assyria 
they  are  recognised  ;  in  those  of  Egypt  they  are  perfectly 
preserved  ;  in  those  of  Etruria  and  Mexico  they  are  trace- 
able. This  wide  diffusion  indicates  a  common  origin, 
both  of  the  race  of  man  and  of  the  symbols  of  astronomy. 
The  love  of  symbols  has  been  considered  as  natural  to 
man  ;  the  creation  amid  which  he  is  placed  is  symbolical. 
Of  this  universal  tendency  the  inventors  of  astronony  seem 
to  have  availed  themselves,  rendering  it  subservient  to 
man's  spiritual  education  by  familiarising  to  his  mind  the 
lofty  truths  of  Divine  revelation." 


42         THE  STORY  OF  THE  STARS. 

"  The  earliest  positive  evidence  of  the  primeval  exist- 
ence of  the  signs  is  in  the  Chinese  Annals,  where  it  is  said 
that  the  Emperor  Yao,  2357  years  before  the  Christian 
era,  divided  the  12  signs  of  the  zodiac  by  the  28  mansions 
of  the  moon  ;  but  it  is  not  said  that  he  invented  them. 
The  Chinese  national  emblem  of  the  dragon  appears  to  be 
the  dragon  of  the  sphere,  which  was  at  that  time  the  polar 
constellation,  the  brightest  star  in  the  dragon's  head  hav- 
ing been  the  Pole  Star  in  the  antediluvian  ages.  The 
Egyptians,  on  whose  early  monuments  the  signs  are 
found,  acknowledged  that  they  derived  their  astronomy 
from  the  Chaldseans.  The  Chaldasans  attributed  their 
science  to  Cannes,  supposed  to  be  Noah.  The  Arabs 
and  Brahmins,  among  whom  astronomy  was  early  culti- 
vated, seem  to  have  derived  it  from  Abraham,  through 
Ishmael,  and  the  children  of  Keturah.  The  Greeks  sup- 
posed their  imperfect  knowledge  of  the  subject  came 
through  the  Egyptians  and  Chaldaeans.  The  Romans  are 
thought  to  have  received  through  the  Etrurians  the  names 
of  the  signs  still  in  use  among  European  nations.  The 
Etrurians  are  considered  to  have  derived  them,  with  their 
other  arts  and  sciences,  from  Assyria.  The  early  Greek 
poet  Hesiod  is  said  to  have  made  use  of  Assyrian  records. 
He  mentions  some  of  the  constellations  by  the  names 
they  now  bear.  Cleostratus  \czrca  500  B.  c]  was  ac- 
quainted with  the  signs,  and  wrote  on  Aries  and  Sagit- 
tarius. A  later  Greek  poet,  Aratus,  described  the  constel- 
lations such  as  we  now  have  them,  and  by  equivalent 
names.  He  gave  neither  history  nor  conjecture  as  to 
their  date,  their  meaning,  or  their  origin.  They  were  to 
him,  as  to  us,  of  immemorial  antiquity." 

The  thoughts  unfolded  in  the  foregoing  extract  are  of 
great  interest,  but  it  is  obvious  that  a  thorough  investiga- 
tion of  this  subject  would  lead  us  far  beyond  the  limits  of 
this  little  volume. 


THE  NUMBER  OF  THE  STARS. 


43 


CHAPTER  VI. 


THE   NUMBER  OF  THE   STARS. 


To  say  much  that  is  definite  about  the  number  of  the 
stars  is  in  one  sense  a  very  difficult  thing  to  do  if  the  idea 
is  to  furnish  any  trust- 
worthy or  adequate 
information  on  the 
subject.  The  words 
of  Holy  Scripture, 
"  Look  now  towards 
heaven,  and  tell  the 
stars,  if  thou  be  able 
to  number  them,"* 
cover  much  more  than 
appears  at  first  sight. 
To  say  that  the  stars 
are  innumerable  is  far 
from  being  a  mere  po- 
etic phrase ;  it  is  in- 
deed no  more  than  a 
prosaic  matter  of 
fact.  Nevertheless  it 
may  probably  surprise 
some  persons  to  be 
told  that  according  to 
the  estimate  of  the 
distinguished  German 

astronomer  Argelander  the  number  of  stars  visible  to  the 
naked  eye  in  the  latitude  of  Berlin  is  only  3256,  and  must 
be  put  no  higher  than  about  5000  in  all  for  the  whole 
heavens.     The  number  to  be  seen  becomes  greater  as  we 


Fig. 


-Orion. 


Genesis  xv.  5. 


44         THE  STORY  OF  THE  STARS. 

approach  the  equator  from  the  middle  latitudes  of  either 
hemisphere,  owing  to  the  wider  expanse  opened  up  to  an 
observer  stationed  at  the  equator.  An  observer  located*  in 
a  place  the  latitude  of  which  is  o°  will  see  in  the  course 
of  the  year  all  the  naked-eye  stars  in  the  heavens. 

Argelander's  totals  arranged  in  magnitudes  are  as  fol- 
lows : — 


Stars. 

ist  magnitude 

= 

20 

2nd 

" 

= 

65 

3rd 

" 

= 

igo 

4th 

t< 

= 

425 

5th 

<( 

= 

1 100 

6th 

'♦ 

= 

3200 

7th 

" 

= 

13,000 

8  th 

(< 

= 

40,000 

9th 

a 

= 

142,000 

This  matter  has  been  made  the  subject  of  estimate  by 
various  observers,  including  especially  the  late  Professor 
Grant  of  Glasgow  and  Karl  Von  Littrow  of  Vienna. 
Their  figures,  though  fairly  accordant  as  regards  naked- 
eye  stars  in  the  aggregate,  differ  a  good  deal,  magnitude 
by  magnitude,  owing  to  there  being  no  recognised  defined 
standards  of  magnitude. 

As  to  this,  however,  it  may  be  remarked  as  a  thing  by 
the  way,  that  Seidel,  a  German  observer  who  has  given 
much  attention  to  the  matter,  has  suggested  the  following 
as  standard  stars  for  the  first  4  magnitudes : — 

1st — o  Aquilge,  a  Virginis,  a  Ononis. 

2nd — a  Ursse  Majoris.  -y  Cassiopeiae,  Algol  (at  max.). 

3rd — 7  Lyrae,  5  Herculis,  Q  Aquilae. 

^ (  p  Herculis,  X  Draconis  (too  bright), 

\  fi  Bootis,  0  Herculis  (too  faint). 

It  may  be  well  to  point  out  that  the  statistics  just  given, 
though  necessarily  somewhat  approximate,  are  not  to  be 


THE  NUMBER  OF  THE  STARS.  45 

regarded  as  imaginary,  though  of  course  to  count  a  num- 
ber of  points  of  light  like  stars  is  not  in  itself  an  easy  task. 
It  may  be  worth  while,  therefore,  to  carry  the  foregoing 
statements  a  little  farther.  A  very  painstaking  astrono- 
mer, also  a  German,  Hels  of  Miinster,  affirmed  that  it  was 
not  possible  to  count  more  than  about  5000  stars  visible  in 
the  sky  available  in  Central  Europe.  Endowed  with  a  sharp 
sight,  and  adopting  various  artifices  (such  as  shutting  out 
all  artificial  light  and  marking  off  by  means  of  a  great 
black  tube  each  region  of  the  sky  under  examination),  he 
found  himself  able  at  Miinster  to  see  5421  stars.  Inas- 
much as  he  could  from  that  one  place  in  the  course  of  a 
year  examine  in  succession  y^hs  of  the  heavens,  he  con- 
cluded that  supposing  the  portion  of  the  Southern  hemi- 
sphere which  he  could  not  see  resembled  in  a  sense  the 
rest  of  the  sky  which  he  could  see,  the  sum  total  of  the 
stars  visible  to  the  naked  eye  would  mount  up  to  about 
6800.  But  it  deserves  notice  that  no  possible  number  of 
stars  which  could  be  counted  would  represent  the  stars 
which  an  eye  could  discern.  The  eye  can  take  notice  of 
more  than  it  can  count,  because  when  any  given  star  im- 
prints itself  upon  the  centre  of  the  retina,  others  whose 
images  fall  upon  the  corners  of  the  eye,  so  to  speak,  seem 
to  vanish.  This  is  a  point  as  to  which  appearances  are 
apt  to  be  very  deceptive.  It  may  be  well  here  to  remark 
that  it  is  important  to  distinguish  clearly  in  the  mind  be- 
tween the  results  of  a  single  gaze  at  the  sky,  the  eye  being 
for  the  while  fixed,  and  a  look  all  round.  In  the  former 
case  it  may  be  taken  that  no  more  than  a  space  of  13°  or 
14°  can  be  taken  in  simultaneously,  whilst  by  moving  the 
eye  methodically  in  successive  directions  the  whole  ex- 
panse of  the  heavens  may  be  brought  under  review. 

Secchi  noted  the  following  experiment  as  one  that  he 
often  tried  with  interesting  results.  After  taking  a  glance 
at  some  particular  part  of  the  heavens  he  would  transfer 


46  THE  STORY  OF  THE  STARS. 

his  eye  to  the  finder  of  the  great  telescope  at  the  Roman 
College  at  Rome,  and  would  see  in  this  subordinate  tele- 
scope, whose  field  was  no  larger  than  ^°,  as  many  stars  as 
were  to  be  seen  in  the  13°  or  14°  grasped  by  the  naked 
eye.  Passing  then  to  his  great  telescope,  armed  with  an 
eye-piece  showing  only  an  arc  of  15',  or  one-fourth  the 
area  of  the  field  of  his  finder,  he  would  still  see  as  many 
stars  as  in  the  finder  ;  proceeding  yet  further  to  diminish 
the  field  by  increasing  the  power,  the  number  of  the  stars 
would  scarcely  diminish,  because,  though  the  area  was 
curtailed,  yet  the  increased  magnifying  power  revealed 
minute  stars  which  had  previously  escaped  notice.  Thus 
it  came  about  that  in  certain  localities  it  was  possible  to 
see  in  a  field  no  more  than  -j\°  in  diameter  as  many  stars 
as  were  visible  to  the  naked  eye  in  a  field  13°  in  diameter. 
This  train  of  thought  will  readily  enable  the  general  reader 
to  realise  the  fact  that  the  larger  our  telescopes  become 
the  more  stars  we  can  discern  ;  in  other  words,  that  as  we 
cannot  say  for  a  certainty  how  large  our  telescopes  might 
become,  so  accordingly  we  cannot  say  when  stars  hitherto 
unseen  will  cease  to  be  invisible  by  becoming  visible.  So 
that  we  may  indeed  say  with  Galileo  that  the  stars  are  z'n- 
nu7Jierable.  i 

The  heavens  are  not  everywhere  equally  rich  ;  in  many 
places  even  with  the  largest  instruments  one  can  find  in  a 
field  of  \°  scarcely  5  or  6  stars  :  it  would  not,  therefore, 
do  to  judge  of  the  number  of  the  stars  by  these  excep- 
tional regions.  An  effort  was  made  by  the  two  Her- 
schels,  Sir  William  in  the  Northern  hemisphere,  and  Sir 
John  in  the  Southern  hemisphere,  to  ascertain  the  possible 
number  of  the  stars.  It  is  easy  to  understand  that  this  is 
one  of  the  most  gigantic  tasks  which  an  astronomer  could 
undertake,  because  it  could  never  be  completed  in  the 
lifetime  of  one  man.  Sir  W.  Herschel  adopted  an  indirect 
method  to  arrive  at  his  results.     Making  use  of  his  20-ft. 


THE  NUiMBER  OF  THE  STARS.  47 

reflector,  he  directed  it  successively  towards  certain  parts 
of  the  heavens,  chosen  in  irregular  order,  of  which  he 
noted  the  right  ascension  and  declination.  These  regions 
were  so  distributed  over  the  heavens  as  in  a  way  to  result 
in  the  sky  being  dotted  over  with  a  network  of  surveying 
stations  equi-distant  from  each  other.  The  field  of  his 
telescope  was  just  J°,  and  the  magnifying  power  120.  He 
counted  in  each  field  the  number  of  stars  visible  in  it ;  in 
particular  places  where  the  number  was  so  great  as  to 
render  counting  impossible  he  made  an  estimate.  Hav- 
ing gathered  together  a  certain  number  of  these  counts, 
or  estimates,  in  a  particular  part  of  the  sky,  he  summed 
up  the  total  number  of  stars  seen,  and  divided  this  total 
by  the  number  of  the  groups.  The  resulting  figure  was 
taken  to  represent  the  mean  average  density  of  the  stars 
in  the  neighbourhood  of  the  place  examined.  This  meth- 
od, the  only  one  possible  in  practice,  has  some  defects  ; 
still,  employed  on  the  large  scale  carried  out  by  Sir  Wil- 
liam Herschel,  it  gave  results  so  far  conclusive  that  no 
more  modern  effort  has  yet  superseded  it.  Of  course  it 
will  often  happen  that  a  certain  locality  will  be  very  rich 
in  stars,  whilst  in  another  like  area,  not  far  off,  there  will 
be  a  great  scarcity  of  stars  ;  still,  taking  rich  and  poor 
neighbourhoods  together,  a  fairly  trustworthy  average  re- 
sult will  be  obtained.  It  has  already  been  stated  that  to 
take  a  census  of  the  whole  heavens  would  be  a  work  so 
vast  that  no  one  man  could  ever  hope  to  accomplish  it  ; 
there  is,  however,  now  in  progress  an  international  photo- 
graphic survey  of  the  heavens,  which,  when  it  is  complete, 
will  go  far  to  fill  up  the  void  in  our  knowledge  which  at 
present  exists  ;  but  before  speaking  of  this  it  will  be  bet 
ter  to  finish  with  the  work  of  the  Herschels  in  this  depart- 
ment of  astronomy.  To  obtain  an  idea  of  it,  it  will  suffice 
to  remember  that  Sir  W.  Herschel  dealt  with  3400  groups. 
These  were  not  all  completely  independent  of  one  another, 


48  THE  STORY  OF  THE  STARS. 

and  they  must  be  reduced  to  the  smaller  number  of  683  in 
order  to  obtain  the  number  of  the  quite  independent 
groups.  Herschel  is  considered  to  have  examined  onl}' 
^^oth  part  of  the  sky  ;  it  would  have  taken  him  83  years 
to  have  gone  over  the  entire  heavens,  allowing  that  he 
could  have  done  100  fields  every  night,  and  could  have 
found  100  favourable  nights  in  every  year.  In  some  re- 
gions the  stars  were  so  numerous  that  Sir  William  counted 
588  in  one  field  of  view,  and,  the  telescope  remaining  sta- 
tionary, field  after  field  quite  as  rich  passed  along  as  in  a 
panorama  for  several  minutes.  At  one  place  he  estimated 
that  he  had  seen  116,000  stars  passing  before  him  in  a 
quarter  of  an  hour  ;  and  that  on  another  occasion  258,000 
stars  passed  in  41  minutes  ;  on  the  other  hand,  in  other 
parts  of  the  heavens  fields  presented  themselves  with  only 
two  or  three  stars  in  them.  The  results  which  Sir  W. 
Herschel  arrived  at  were  published  in  1785.  Nearly  50 
years  later  his  son,  who  went  out  to  the  Cape  of  Good 
Hope  for  the  express  purpose  of  carrying  on  observations 
in  the  Southern  hemisphere,  took  up  again  this  very  self- 
same question  of  the  numbering  of  the  stars.  His  results, 
equally  as  interesting  as  his  father's,  differed  from  them  in 
this  particular,  that  the  Southern  hemisphere  is  less  uni- 
formly decked  with  stars  than  the  Northern  hemisphere, 
and  bare  places  are  more  common. 

By  a  computation  based  on  the  results  of  gauging 
both  hemispheres.  Sir  John  Herschel  found  that  the  total 
number  of  stars  visible  in  an  18-inch  reflector  cannot  be 
less  than  5J  millions,  but  Struve,  interpreting  Sir  W.  Her- 
schel's  observations  in  the  light  of  his  own,  estimated  that 
more  than  20  millions  of  stars  were  within  the  grasp  of  a 
reflector  of  the  named  dimensions. 

The  most  cursory  examination  of  the  heavens  will 
make  it  clear  that  the  stars  are  very  unequally  distributed  ; 
that  in  some  parts  they  are  very  much  more  closely  ar- 


THE  NUMBER  OF  THE  STARS.  49 

ranged  than  in  others,  and  that  this  is  true  whether  we 
consider  their  absolute  number  or  their  individual  bright- 
ness. Various  attempts  have  been  made  to  frame  specu- 
lations as  to  the  causes  and  meaning  of  these  facts,  but  it 
is  obvious  that  all  such  speculations  must  be  more  or  less 
useless  and  unprofitable.  I  may  have  something  more  to 
say  on  this  subject  when  we  come  to  deal  with  that  won- 
derful mass  of  stars  which  we  call  the  Galaxy,  or  Milky 
Way,  but  an  investigation  as  to  the  "  how  "  or  the  "  why  " 
there  are  more  stars  to  be  seen  in  some  places  than  in 
others  would,  in  the  present  state  of  our  knowledge,  lead 
to  no  very  definite  or  satisfactory  results. 

A  few  words  about  the  International  Photographic 
Survey  of  the  Heavens  which  is  now  in  progress.  This 
took  its  origin  from  a  Conference  of  Astronomers,  repre- 
senting 16  different  nationalities,  which  met  at  the  Paris 
Observatory  in  April,  1887,  on  the  invitation  of  the  Acad- 
emy of  Sciences  of  France.  The  basis  on  which  the 
undertaking  was  started  was  in  substance  defined  as  fol- 
lows : — (i)  That  the  progress  made  in  astronomical  pho- 
tography demands  that  the  astronomers  of  the  present 
day  should  unite  in  obtaining  a  permanent  record  of  the 
heavens  by  means  of  photography.  (2)  That  the  work 
should  be  carried  out  at  selected  stations,  and  with  instru- 
ments which  should  be  identical  in  size  and  other  essen- 
tial features.  (3)  That  the  principal  object  to  be  aimed 
at  is  to  secure  a  chart  of  the  heavens  for  the  present 
epoch,  and  therewith  data  for  determining  with  the  great- 
est possible  accuracy  the  positions  and  brightness  of  all 
stars  down  to  a  given  magnitude,  the  ultimate  idea  being 
>hat  the  information  thus  obtained  should  be  so  preserved 
as  to  be  available  in  future  years  for  determining  whether 
changes  of  position  or  brightness  have  occurred  in  re- 
spect of  any  given  stars.  These  preliminary  principles 
having  been  accepted  by  the  Conference,  which  comprised 


50         THE  STORY  OF  THE  STARS. 

20  representatives  for  France,  8  for  England  and  the 
British  Colonies,  6  for  Germany,  3  each  for  Russia,  Hol- 
land, and  the  United  States,  2  each  for  Austria,  Sweden, 
and  Denmark,  and  i  each  for  Belgium,  Italy,  Spain,  Portu- 
gal, Switzerland,  Brazil,  and  Argentina,  a  committee  was 
appointed  to  consider  and  report  upon  the  form  and  size 
of  the  instruments  to  be  used  and  the  range  of  magnitudes 
to  be  embraced.  After  a  large  amount  of  anxious  inquiry 
and  debate,  it  was  eventually  decided  that  the  instruments 
employed  should  be  exclusively  refractors  of  1 1  inches 
aperture,  and  rather  more  than  1 1  feet  focal  length,  giving 
a  field  of  2°  square,  the  photographic  plates  being  6^ 
inches  square,  and  showing  an  effective  square  {reseau)  of 
5^  inches,  with  lines  \  inch  apart. 

The  necessary  instruments  have  been  provided,  chiefly 
at  the  cost  of  the  Governments  of  the  respective  countries, 
and  the  survey  is  now  well  in  hand  at  the  following  19  ob- 
servatories— Helsingfors,  Potsdam,  Oxford,  Greenwich, 
Paris,  Vienna,  Bordeaux,  Toulouse,  Catane,  Algiers,  San 
Fernando,  Chapultepec,  Tacubaya,  Rio  de  Janeiro,  Santi- 
ago, Sydney,  Cape  of  Good  Hope,  La  Plata,  and  Mel- 
bourne. These  observatories  range  in  latitude  from  60° 
N.  to  38°  S.,  and  may  be  considered  as  conveniently 
placed  for  embracing  the  whole  sky.  It  is  scarcely  neces- 
sary to  add  that  the  work  undertaken  is  one  of  enormous 
magnitude,  and,  though  not  actually  difficult,  requires  in 
a  high  degree  the  services  of  observers  well  endowed  with 
the  virtues  of  patience  and  carefulness.  The  work  will, 
of  course,  occupy  several  years. 


DOUBLE  STARS. 


51 


CHAPTER   VII. 

DOUBLE  STARS. 


We  have  hitherto  been  considering  the  stars  as  iso- 
lated points  of  light  dotted  hither  and  thither  all  over  the 
heavens  and  as  if  they  had  no  connection  one  with  an- 
other.    These   suppositions   are   only  true  in  a  qualified 


Fig.  5.— a  Herculis  (double  star). 

sense,  for  the  telescope  reveals  the  fact  that  no  inconsidr 
erable  number  of  the  stars  which  we  regard  as  simple 
points  of  light  are  in  reality  2  (or  in  some  cases  several) 
single  stars  which  are  so  close  together  as  to  appear  to 
the  naked  eye  to  be  one. 


52         THE  STORY  OF  THE  STARS. 

The  proximity  of  one  star  to  another  might  in  any- 
given  case  only  be  an  effect  of  perspective  and  not  an 
actual  fact.  For  instance,  a  man  standing  on  the  top  of  a 
straight  road  which  led  up  a  hill  might  see  2  men  ap- 
proaching him,  seemingly  walking  shoulder  to  shoulder, 
as  if  they  were  2  friends  engrossed  in  conversation, 
whereas  in  reality  they  might  be  isolated  individuals  walk- 
ing up  the  hill,  each  on  his  own  account,  perhaps  50  yards 
apart.  On  the  other  hand,  if  the  man  at  the  top  saw  the 
other  2  men  cross  from  one  side  of  the  road  to  the  other 
simultaneously,  and  that  as  one  turned  his  head  askew, 
apparently  to  look  at  some  distant  object,  the  other  did 
the  same  thing,  he  might  justly  infer  that  the  two  were 
really  friends  and  were  really  walking  side  by  side. 

The  foregoing  illustrations  will  define  with  perfect  ac- 
curacy the  difference  between  what  is  called  an  "  optical " 
double-star  (that  is,  2  stars  which  seem  to  be  linked  to- 
gether because  of  the  effect  of  perspective)  and  a  "  binary  " 
double-star ;  that  is,  2  stars  which  not  only  seem  to  be 
linked  together  but  truly  are  so.  These  last-named  are 
often  spoken  of  as  "  physical  doubles,"  or  2  stars  physically 
connected.  To  determine  in  any  given  case  whether  a 
pair  of  stars  belong  to  the  one  class  or  the  other  is  a  mat- 
ter involving  both  delicate  observations  and  laborious  cal- 
culations. More  than  a  century  and  a  quarter  ago  Michell 
suspected  that  there  might  be  a  physical  connection  sub- 
sisting between  certain  stars  by  considering  the  probable 
chance  of  producing  a  purely  accidental  combination  if  a 
batch  of  stars  were,  so  to  speak,  promiscuously  thrown 
haphazard  into  space.  He  found  that  the  chances  of 
bringing  together  stars  such  as  the  Pleiades,  of  their 
brightness  and  at  their  distance,  was  500,000  to  i,  of  1500 
stars  visible.  The  improbability  became  much  greater  if 
the  inquiry  was  based  upon  the  case  of  stars  of  the  2nd 
and  3rd  magnitudes  and  within  a  few  seconds  of  arc  of 


DOUBLE  STARS.  53 

one  another.     Yet  in  point  of  fact  we  have  several  exam- 
ples of  this  kind,  such  as  a  Centauri  and  a  Geminorum. 

But  probability  does  not  suffice  to  establish  the  truth 
of  a  fact.  One  draws  a  much  more  conclusive  argument 
from  a  consideration  of  the  actual  proper  motions  of  the 
stars  where  such  can  be  detected.  If  the  stars  were  acci- 
dentally brought  together,  as  they  are  generally  of  differ- 
ent magnitudes,  their  proper  motions,  both  real  and  ap- 
parent, would  also  differ ;  consequently  with  the  lapse  of 
time  they  ought  to  separate  from  one  another.  Yet  it 
happens  that  many  of  these  stars,  though  exhibiting  con- 
siderable actual  motion,  preserve  very  much  the  same  dis- 
tance from  one  another  during  an  extremely  long  interval 
of  time.  Such  are  the  two  stars  composing  a  Centauri,  a 
Geminorum,  y  Virginis,  ^  Ursas  Majoris,  and  a  great  num- 
ber of  others,  pairs  of  unequal  size,  a  Centauri,  the  two 
constituent  stars  of  which  were  separable  with  difficulty 
in  a  telescope  100  years  ago,  has  such  a  considerable 
proper  motion  that  the  two  stars  ought  now  to  have  be- 
come separated  by  an  interval  of  6  minutes  if  the  proper 
motion  of  the  one  w^ere  not  shared  in  by  the  other.  This, 
perhaps,  would  not  always  be  an  unfailing  criterion,  be- 
cause it  might  so  happen  that  the  proper  motions  only  ex- 
hibited small  differences,  notwithstanding  the  extent  and 
reality  of  the  difference.  What,  after  all,  would  in  any 
given  case  plainly  decide  the  question  would  be  the  posi- 
tive fact  (where  it  could  be  established)  that  one  star 
turned  around  the  other  in  a  closed  orbit  in  seeming  ac- 
cordance with  the  recognised  principles  of  the  law  of 
gravitation.  This  great  discovery  has  indeed  been  made, 
and  we  owe  it  to  Sir  William  Herschel.  When  that  re- 
markable man  had  sufficiently  perfected  his  instruments, 
so  that  he  could  penetrate  into  the  depths  of  space  in  a  way 
never  before  attempted  by  any  of  his  predecessors,  he  set 
himself  the  task  of  seeking  to  discover  stellar  parallax,  or 


54         THE  STORY  OF  THE  STARS. 

the  actual  distances  of  the  stars  from  the  earth.  He  se- 
iected  for  his  purpose  certain  large  stars  which  were 
accompanied  by  small  companions  at  a  distance  of  only  a 
few  seconds  of  arc.  He  measured  these  distances  with 
great  care  by  means  of  an  instrument  of  his  own  invention 
called  a  "  micrometer,"  which  also  enabled  him  to  deter- 
mine the  angle  made  by  a  line  passing  through  two  stars 
with  the  meridian.  He  called  this  angle  the  "  angle  of 
position  "  of  the  two  stars,  regarding  the  larger  of  them 
as  the  determining  centre  of  the  arc  on  which  the  meas- 
orement  was  founded.  If  there  had  been  any  annual  par- 
allax— that  is  to  say,  any  apparent  displacement  of  the 
stars  with  respect  to  the  celestial  background,  as  a  result 
of  viewing  the  stars  from  opposite  points  of  the  earth's 
orbit  at  6-monthly  intervals — that  parallax  would  have 
been  discoverable  because  there  would  have  been  disclosed 
a  variation  in  the  distance  or  angle,  comparing  one  time 
with  another  separated  by  the  interval  of  6  months.  How- 
ever, after  numerous  and  painstaking  researches,  carried 


Fig.  6.—C  HercuHs  (1865).  Fig.  7.—^  Herculis  (1871). 

out  with  every  attention  to  detail,  Herschel  could  not  sat- 
isfy himself  that  he  had  obtained  any  proofs  of  change, 


DOUBLE  STARS. 


55 


and  he  gave  up  the  work  for  a  time  in  despair.  Having 
afterwards  improved  his  instrumental  means,  he  resumed 
his  labours,  hoping  for  better  results.  Great  was  his  sur- 
prise to  find  that  some  of  the  stars  which  he  had  formerly- 
seen  double  had  become  single,  the  junior  member  having 
disappeared,  whilst  others  had  evidently  changed  both 
their  angular  position  and  their  distance.  Though  all 
hope  of  discovering  an  annual  parallax  seemed  to  have 
vanished,  at  least  he  had  obtained  traces  of  a  parallax  of 
another  sort,  due  either  to  a  general  movement  of  the 
whole  system  or  to  some  special  movement  appertaining 
to  particular  stars.  Michell's  old  idea  seems  to  have  re- 
curred to  Herschel's  mind  and  to  have  stimulated  him  to 
further  effort,  and  after  several  additional  years  of  pains- 
taking and  laborious  work,  at  length  in  1802  he  found 
himself  in  a  position  to  announce  to  the  scientific  world 
his  grand  discovery  that  there  existed  systems  formed  by 
pairs  of  stars  revolving  about  each  other  in  regular  elliptic 
orbits.  He  coined  the  word 
"  binary "  and  gave  it  to 
these  stars,  to  distinguish 
them  from  mere  optical 
double-stars,  which  do  not 
exhibit  any  mutual  periodic 
changes  of  place. 

The  interval  that  elapsed 
between  Sir  W.  Herschel's 
abandonment  of  his  first  re- 
searches and  his  renewal  of 
work  was  about  25  years. 
This  is  a  period  quite  suffi- 
cient to  enable  the  motion  of 
many  binary  stars  to  become  evident  to  the  senses,  and 
accordingly  no  fewer  than  about  50  stars  were  noticed  by 
Herschel  to  have  undergone  change  during  the  time  that 


Fig.  8.—^  HercuHs  (1883). 


56 


THE  STORY  OF  THE  STARS. 


his  operations  were  suspended.  True  that  his  stars  had, 
for  the  most  part,  only  had  time  to  traverse  a  portion  of 
their  orbits,  but  more  than  90  years  having-  elapsed  since 
Herschel's  announcement  of  1802,  it  follows  that  a  certain 
number  of  binary  stars  have  not  only  gone  entirely  round 
in  their  orbits  once,  but  some  of  them  have  done  so  almost 
twice,  and  the  form  and  dimensions  of  their  orbits  are 
now  fairly  well  understood.  To  cut  a  long  story  short,  it 
may  be  stated  that  fully  200  pairs  of  stars  are  now  recog- 
nised to  be  in  motion  round  one  another  in  obedience  to 
laws  probably  identical  with  what  are  known  as  the  laws 
of  gravitation,  though  for  obvious  reasons  their  orbits  have 
not  all  been  investigated  with  equal  completeness  and 
accuracy.  The  following  are  the  names  and  particulars 
of  a  few  of  the  binary  stars  with  periods  of  less  than  100 
years,  the  nature  of  whose  movements  has  been  ascer- 
tained with  fair  certainty  : — 


Name  of  Star. 

Period. 

Date  of  Last 
Passage. 

Years. 

42  Comae  Berenices 

25 

1870 

<■  Herculis 

34 

1864 

77  Coronce 

41 

189I 

^2  Herculis 

45 

1880 

Sirius 

49 

1893 

C  Cancri 

59 

1868 

1  Ursse  Majoris 

60 

1875 

a,  Centauri 

77 

1875 

7  Coronas 

85 

1840 

70  (/)  Ophiuchi 

94 

1808 

Sir  W.  Herschel's  original  observations  had  reference 
only  to  pairs  of  stars,  but  the  further  attention  which  has 
been  given  to  this  subject  of  late  years  has  resulted  in 
the  discovery  of  the  fact  that  in  certain  cases  there  exist 
systems  of  stars  in  triplets,  each  member  of  which  sys- 


DOUBLE  STARS.  57 

tern  has  a  relation  to  the  other  two,  which  justifies  their 
being  called  not  simply  triple  stars  but  "  ternary  "  stars. 
^  Cancri  is  an  object  of  this  type. 

It  must  be  added,  by  way  of  caution,  that  though 
movement  on  the  part  of  a  pair  of  stars  during  a  course 
of  years  is  prima  facie  3.  proof  of  physical  connection 
involving  motion  in  a  closed  orbit,  yet  this  must  not  be 
regarded  as  a  rule  of  universal  application.  A  mere  an- 
gular displacement  may,  in  a  given  case,  be  the  effect  of 
individual  proper  motion  on  the  part  of  one  or  both  of  the 
stars  of  a  pair,  and  not  the  effect  of  a  central  force.  From 
this  it  will  follow  that  sometimes  the  positions  successive- 
ly occupied  by  the  principal  star  will  not  exhibit  the  line 
of  a  sensible  curve.  Flamsteed's  6ist  star  in  Cygnus 
seems  to  be  one  of  this  character  ;  it  is  moving,  but  its 
motion  is  in  a  straight  line. 

Before  passing  away  from  the  subject  of  double  stars, 
a  word  should  be  said  about  the  remarkable  circum- 
stances of  2  stars  which  are  well  known  by  reason  of 
their  great  intrinsic  brilliancy— Sirius  and  Procyon.  Both 
these  stars  are  subject  to  peculiar  disturbances  of  place, 
which  long  excited  the  surprise  and  curiosity  of  astrono- 
mers. It  was  suggested  that  these  disturbances  were  due 
to  the  presence  of  some  invisible  satelHte,  and  in  the  case 
of  Sirius  this  surmise  has  proved  well  founded.  In  1862 
Alvan  Clark,  a  well-known  American  optician,  found  near 
Sirius  a  minute  companion,  the  existence  of  which  has 
enabled  astronomers  to  explain  some,  though  perhaps  not 
ail,  of  the  irregularities  found  to  exist  in  the  positions  of 
the  primary  star  at  different  times.  Arising  out  of  this 
is  the  further  conclusion  that  this  faint  attendant,  which 
has  only  y^^jj-  of  the  light  of  Sirius,  possesses  a  mass 
more  than  ^  of  Sirius.  In  other  words,  unless  it  does 
thus  really  approximate  in  mass  to  Sirius  itself,  it  is  not 
capable    of    accomplishing    the    observed    disturbances. 


58         THE  STORY  OF  THE  STARS. 

That  disturbances  are  traceable  in  the  movements  of 
Sirius  is  no  new  idea,  for  the  great  German  astronomer, 
Bessel  of  Konigsberg,  as  far  back  as  1844,  not  only  no- 
ticed their  existence  but  suggested  the  presence  of  an  in- 
visible perturbing  body,  belonging  to  the  system  of  Sirius, 
as  an  explanation  of  the  fact  that  the  proper  motion  of 
Sirius  takes  place  not  in  a  regular  line,  but  in  an  irregular 
sinuous  line.  Accordingly,  he  suggested  that  this  very 
bright  star  possessed  a  dark  satellite.  Other  astronomers 
worked  at  the  idea,  and  may  be  said  to  have  paved  the 
way  for  the  actual  discovery  of  the  satellite  by  Clark. 

A  very  interesting  question  often  presents  itself  to 
students  of  astronomy,  who  meditate  on  what  they  have 
seen  after  they  have  examined  double  stars.  The  ques- 
tion may  be  put  in  this  form  :  We  on  the  earth  are 
placed  on  a  certain  moving  body  called  a  planet,  which  is 
one  of  a  number  of  planets  circulating  round  the  sun  as 
their  chief  ruler  or  centre.  Is  this  state  of  things  unique  ? 
Or,  on  the  other  hand,  do  other  suns  exist  ?  Or,  to  be 
more  precise,  do  other  bodies  exist  in  the  universe  which 
are  centres  of  life  and  motion  analogous  to  our  sun  ?  No 
one  who  has  seen  a  bright  double  star,  with  its  one  or 
more  companions,  and  still  more,  no  one  who  has  seen 
the  many  bright  stars  with  companions  which  are  to  be 
found  scattered  up  and  down  the  heavens,  can  doubt 
that  the  answer  to  the  above  main  question  must  un- 
doubtedly be  in  the  affirmative.  In  other  words,  that 
there  are  in  the  universe  many  suns,  each  with  its  own 
cortege  of  planets,  and  not  one  sun  only.  Much  beyond 
this,  however,  we  cannot  go.  One  thing  is  not  a  matter 
of  speculation.  Whereas  our  planets  revolve  round  the 
sun  in  orbits,  which  though  not  truly  circular,  are  yet  not 
very  eccentric  ;  that  is,  do  not  depart  much  from  the  cir- 
cular form,  yet  in  the  cases  of  the  binary  stars,  the  orbits 
of  all  that  are  known  depart  very  much  indeed  from  the 


FAMILY   PARTIES   OF   STARS.  59 

circle.  Secchi  has  well  pointed  out  that  if  we  consider 
for  a  moment  what  is  involved  in  the  existence  of  lumi- 
nous systems  of  stars,  we  may  well  be  struck  with  the  in- 
ferences which  necessarily  follow.  In  the  case  of  a  sys- 
tem the  form  of  whose  orbit  is  very  eccentric  (such  as 
a  Centauri),  any  attendant  planets  must  be  warmed  some- 
times by  2  suns  very  near,  sometimes  by  one  sun  very 
near,  and  by  another  very  far  off.  Who  can  calculate 
the  transformations  of  life  which  go  on  under  such  cir- 
cumstances without  remembering  the  wisdom  of  Him 
who  often  with  small  apparent  means  is  able  to  bring 
about  an  infinite  variety  of  results  ?  Add  to  this  the  fact 
that  double  stars  very  often  exhibit  different  and  comple- 
mentary colours.  The  imagination  of  even  a  poet  would 
be  incapable  of  describing  to  us  the  phases  of  a  day 
illuminated  by,  say,  a  red  sun,  and  of  a  night  illuminated 
by,  say,  a  green  sun  ;  or  of  a  day  in  which  2  suns  of  dif- 
ferent colours  competed  with  one  another,  whilst  the 
night  was  ushered  in  by  a  golden  twilight  and  the  next 
morning  was  preceded  by  a  blue  dawn.  But  I  do  not 
wish  in  this  chapter  to  drift  into  star  colours,  for  that  is  a 
subject  of  sufficient  importance  to  deserve  a  chapter  to 
itself. 


CHAPTER   VIII. 

FAMILY   PARTIES    OF   STARS. 

The  subject  matter  of  the  preceding  chapter  will  nat- 
urally suggest  the  idea  that  if  one  naked-eye  star  is  found 
telescopically  to  consist  really  of  2  stars,  why  not  another 
of  3  stars  or  4  stars,  or  more,  in  close  association  physic- 
ally or  apparently  ?  And  such,  indeed,  is  the  case.  We 
have,  accordingly,  plenty  of  triple  stars,  some  quadruples, 
some  quintuples,  some  sextuples,  and  so  on — many  of 


6o 


THE  STORY  OF  THE  STARS. 


them   very  picturesque  to  look  at  through  a  telescope. 

Amongst  the  triple  stars  within  the  easy  reach  of  amateurs 
armed  with  small  telescopes 
may  be  mentioned  Flamsteed's 
II  Monocerotis,  12  Lyncis,  and 
51  Librae.  The  following  are 
quadruples  : — tt'  Canis  Majoris, 
8'^  LacertcB.  /3  Lyrse  is  a  quin- 
tuple. Again  there  are  some 
stars  which  comprise  so  many 
constituents  that  they  can  best 
be  described  as  "  multiples  "  ; 
such  are  e  Lyrae  and  o-  Orionis. 

IG.  9.— e     yrae.  j^  ^.^j  ^^  ^^^^  ^^^^  ^y^^  ^^_ 

gravings  that  each  of  these  exhibits  a  double  system  of 
stars,  so  that  e  Lyrae  may  be  called  a.double-double,  whilst 
a  Orionis  is  a  double-triple.     The  former  object  comprises 


Orionis. 


FAMILY  PARTIES  OF  STARS. 


6i 


one  pair  of  stars  of  mags.  5  and  6|,  whilst  the  second  pair 
are  5  and  5i  respectively.  There  seems  every  reason  to 
suppose  not  only  that  the  2  stars  of  each  pair  constitute 
a  binary  system  (each  star  revolving  round  the  other), 
but  that  each  pair  taken  together  revolves  round  the 
other  pair,  thus  constituting  a  double-binary,  or  a  system 


Fig.  I1.—9  Orionis. 

of  mutual  association  of  great  complexity.  Between  the 
2  main  pairs  there  are  several  smaller  stars.  Many  tele- 
scopes will  show  3,  and  Professor  Hall,  in  America,  has 
made  the  3  into  7,  but  his  additional  stars  are  very  faint 
indeed,  and  can  only  be  seen  in  the  very  largest  telescopes, 
e  I.yrse  is  on  the  frame  of  the  Lyre,  i^°  N.  E,  of  the  very 
bright  star  Vega. 

The  group  forming  a-  Orionis,  whilst  it  bears  a  certain 


62  THE  STORY  OF  THE   STARS. 

farnily  resemblance  to  e  Lyrce,  differs  from  it  in  the  respect 
that  we  have  no  knowledge  of  any  of  the  stars  being 
linked  together  so  as  to  constitute  a  moving  system,  a- 
Orionis  may  be  easily  found,  as  it  forms  the  southern  ver- 
tex of  a  triangle  with  the  2  last  stars  (^  and  e)  in  Orion's 
Belt ;  and  it  is  rather  less  than  a  degree  from  (  in  the 
direction  of  /3. 

Orion  contains  another  multiple  star  of  great  interest 
known  as  6  Orionis.  In  this  case  there  are  6  stars,  the 
four  most  conspicuous  of  which  make  a  trapezium  at  dis- 
tances not  very  unequal.  The  5th  and  6th  stars  are  fainter, 
and  lie  just  outside  the  boundary  lines  of  the  trapezium. 
In  this  case  the  component  stars  are  not  organised  in 
pairs,  and  do  not  appear  to  constitute  a  system  physically 
connected.  6  Orionis  is  in  the  midst  of  the  *'  Great  Nebula 
in  Orion,"  of  which  more  anon.  Perhaps  it  might  even 
be  said  to  form  a  part  of  the  nebula. 


CHAPTER   IX. 

COLOURED    STARS. 

Most  persons  would  say  on  a  casual  glance  that  the 
stars  are  specks  or  points  of  white  light,  and  so  no  doubt 
the  majority  of  them  are ;  but  more  attentive  examina- 
tion will  disclose  the  fact  that  a  very  considerable  number 
of  them  exhibit  definite  colours,  though  those  in  which 
any  colour  is  very  pronounced  are  in  a  great  minority. 
The  student  who  is  familiar  with  the  intense  colours  of 
the  solar  spectrum*  will  be  disappointed  if  he  expects  to 
find  amongst  the  stars  many  colours  as  pronounced  as 
those  which  he  sees  in  the  solar  spectrum.  Neverthe- 
less, it  is  possible  in  a  general  way  to  find  here  and 
there   stars  which  if  they  were  all  brought  together  in 


COLOURED  STARS.  63 

a  row  would  constitute  some  similitude  of  the  solar  spec- 
trum. 

There  are  many  difficulties  in  the  way  both  of  observ- 
ing and  of  recording  the  colours  of  stars,  and  this  ex- 
plains the  discrepancies  in  the  accounts  put  forth  by  dif- 
ferent observers.  In  the  first  place,  people's  eyes  are 
differently  constituted ;  some  eyes  are  more  capable  than 
others  of  accurately  appreciating  and  describing  a  colour. 
Some  eyes,  indeed,  as  is  well  known,  are  totally  mcapable 
of  appreciating  certain  colours  at  all.  Possessors  of  such 
eyes  are  said  to  be  "colour-blind."  But,  disregarding  ex- 
treme cases  of  this  sort,  it  is  quite  certain  that  ordinary 
eyes  will  differ  not  a  little  in  appreciating  a  given  colour. 
It  suffices  to  visit  a  picture  gallery  and  take  note  of  the 
differences  in  the  copies  of  one  and  the  same  original  pic- 
ture which  are  being  made  by  different  copyists,  to  realise 
the  fact  that  particular  hues  in  the  original  are  reproduced 
in  a  very  different  way  by  the  different  persons. 

Then,  again,  the  quality  of  the  glass  of  the  telescope 
employed  influences  much  the  apparent  colours  of  the 
objects  looked  at ;  and  still  greater  is  the  effect  of  the  good 
or  bad  grinding  of  the  lenses.  In  other  words,  lenses 
made  of  very  pure  glass  and  very  accurately  ground  and 
polished  will  yield  images  and  indications  of  colour  which 
will  be  much  more  true  to  nature  than  the  indications 
afforded  by  inferior  glass  inaccurately  figured.  It  is  a 
very  noteworthy  fact  that  metallic  mirrors  always  give  to 
objects  seen  through  them  a  reddish  tinge.  This  is  strik- 
ingly brought  out  in  connection  with  Sir  John  Herschel's 
observations  of  red  stars.  To  many  of  these  objects  he 
has  attached  such  qualifying  words  as  "  carmine,"  "  ruby," 
"intense  crimson,"  where  ordinary  observers  employing 
ordinary  telescopes  would  see  only  ordinary  red  hues. 
Nor  is  magnifying  power  entirely  an  unimportant  matter; 
with  a  low  power  white  will  dominate,  and  other  tints  will 


64  THE    STORY   OF   THE   STARS. 

in  a  measure  be  lost,  because  no  star  is  absolutely  mono- 
chromatic ;  on  the  other  hand,  a  high  magnifying  power 
diminishes  the  total  light,  and,  exaggerating  the  dimen- 
sions of  the  spurious  discs,  renders  the  colours  more  easily 
distinguishable.  Again,  the  state  of  the  atmosphere  and 
the  proximity  of  a  star  to  the  horizon  greatly  affect  its  ap- 
pearance. It  is  only  when  a  star  is  well  up  in  the  heavens 
above  the  horizon  that  its  true  colour,  whatever  it  may  be, 
can  be  noted,  because  near  the  horizon  all  celestial  objects 
apparently  acquire  red  or  orange  hues,  which  do  not  really 
belong  to  them. 

Perhaps  the  greatest  of  all  the  difficulties  which  beset 
the  observer  who  wishes  to  make  an  accurate  record  of 
star  colours,  is  the  difificulty  of  providing  and  using  a 
standard  of  colour  for  comparisons.  Such  a  standard  is 
furnished  naturally  by  the  solar  spectrum  ;  but  astrono- 
mers have  hitherto  been  altogether  bafifled  in  their  at- 
tempts to  reproduce  the  prismatic  colours  in  such  a  way 
that  they  can  be  rendered  practically  available  in  the  dark- 
ness of  night,  side  by  side  with  the  image  of  a  star  pro- 
duced at  the  eye-end  of  a  telescope.  There  is  herein,  in 
point  of  fact,  a  double  difficulty  :  that  which  may  be  called 
the  manual  or  mechanical  difficulty  just  alluded  to,  and 
that  which  arises  from  the  fact  that  the  artificial  light  em- 
ployed by  night  being  yellow,  injures  the  neutrality  of  the 
eye  and  falsifies  all  artificial  colours.  It  was  with  the  idea 
of  getting  over  these  difficulties  that  Secchi  proposed  to 
make  use  of  an  electric  spark,  which,  if  derived  from  dif- 
ferent substances,  would  give  for  each  of  them  a  different 
hue,  but  I  am  not  aware  that  any  attempt  has  ever  been 
made  to  put  this  idea  into  practice. 

Single  stars  of  a  red  or  orange  hue  are  not  uncommon, 
but  isolated  blue  or  green  stars  are  very  rare.  Indeed, 
/3  Librae  appears  to  be  the  only  conspicuous  star  which  is 
green.     In  the  case,  however,  of  double  stars  it  is  much 


COLOURED   STARS. 


65 


more  easy  to  define  their  colours,  for  in  many  mstances 
they  exhibit  very  well-marked  colours,  and  frequently  the 
colours  of  the  2  stars  are  what  are  called  "  complemen- 
tary." The  reader  may  be  reminded  that  this  is  a  tern^ 
applied  by  physicists  to  the  colours  which,  when  united, 
make  white  light.  In  order  to  obtain  a  strictly  exact  idea 
of  what  these  colours  are  recourse  must  be  had  to  a  spe- 
cial instrument  of  which  several  kinds  have  been  con- 
trived. But  for  the  elementary  purposes  of  this  work  it 
will  suffice  to  state  that  the  principal  pairs  of  colours  which 
are  mutually  complementary  are  red  and  green,  orange 
and  blue,  and  yellow  and  violet.  The  intermediate  tints 
are  too  innumerable  to  be  described  in  words,  and  they 
can  only  be  realised  by  instrumental  means. 

When  we  speak  of  double  stars  as  exhibiting  different 
colours  it  is  not  permissible  in  all  cases  to  regard  the 
colours  as  an  optical  illusion  or  an  effect  of  contrast,  for 
in  some  instances  certainly  the  colours  are  an  actual 
physical  reality.  We  may  draw  this  conclusion  in  some 
cases  from  the  circumstance  that  the  colours  seen  are  not 
always  complementary  ;  and  in  other  cases  from  the  fact 
that,  by  concealing  the  principal  star  by  means  of  a  bar 
in  the  eye-piece,  formed  of  watch-spring  or  something  of 
that  sort,  we  shall  notice  that  the  companion  star,  when 
thus  cleared  of  the  effects  of  its  primary,  preserves  its 
colour  unchanged. 

The  following  may  be  mentioned  as  good  examples  oi 
coloured  pairs '. — 


77  Cassiopeise 
a  Piscium 
7  Andromedae 
(  Cancri  .  . . 
€  Bootis  . .  . 
^  Coronae . . . 
5 


Large  Star. 

. .  Yellow  . . . 

. .  Pale  Green 

. .  Orange  . . . 

. .  Orange  .  . . 

. .  Pale  Orange 

..  White      ., 


Companion  Star. 
Purple 

Blue  (or  var.) 
Green 
Blue 

Sea  Green* 
Blue 


66  THE  STORY  OF  THE  STARS. 


a  Herculis 

. .   Orange  . . . 

. . .   Emerald  Green 

/SCygni    ...      . 

. .   Yellow  . . . 

. . .   Sapphire  Blue 

(T  Cassiopeias      . 

. .   Greenish 

. . .    Bright  Blue 

Secchi  compiled  the  following  list  of  conspicuous  stars 
of  the  colours  stated  : —  White,  Procyon,  Altair ;  Blue, 
Sirius,  Vega,  Castor,  Regulus ;  Yellow,  Capella,  Pollux, 
a  Ceti ;  Orange,  Aldebaran,  Aicturus,  Betelguese  ;  Ruddy, 
Antares,  a  Hercuhs. 

Kriiger,  an  experienced  German  observer,  has  given 
the  following  list,  which,  it  will  be  seen,  is  not  wholly 
in  accord  with  Secchi's : —  White,  Sirius,  Altair,  Regu- 
lus ;  Yellow,  Capella,  Pollux,  Arcturus ;  Orange  or  Red, 
a  Herculis,  Betelguese. 

All  the  really  red  stars — that  is,  stars  of  pronounced 
depth  of  colour — are  comparatively  small  in  size — scarcely, 
if  at  all,  visible  to  the  naked  eye.  There  are  a  few — per- 
haps half  a  dozen — to  which  the  designation  "  carmine  " 
may  be  applied,  but  the  bulk  of  the  so-called  red  stars  are 
more  orange  than  red.  I  shall  have  something  more  to 
say  about  some  of  these  in  the  chapter  on  *'  Variable 
Stars." 

The  question  of  whether  the  stars  vary  in  colour  has 
attracted  some  attention,  but  the  evidence  is  on  the  whole, 
meagre  and  inconclusive.  From  a  passage  in  Seneca,  an 
ancient  Roman  writer,  it  has  been  inferred  that  he  wished 
it  to  be  understood  that  in  his  day  Sirius,  the  Dog  Star, 
was  red,  whereas  now  it  is  white,  or  bluish-white.  Ptolemy 
seems  also  to  have  regarded  Sirius  as  a  red  star,  and  to 
have  used  a  v^ord  to  describe  it  which  he  also  applied  to 
Pollux.  Now  Pollux  is  certainly  a  reddish-yellow  star  in 
the  present  day,  and  if  it  and  Sirius  could  ever  have  been 
appropriately  designated  by  the  same  adjective  of  colour, 
then  the  conclusion  follows  as  a  matter  of  course  that 
Sirius  no  longer  exhibits  the  colour  it  once  did.     Capella 


MOVING  STARS.  67 

is  perhaps  another  star  which  has  changed  from  red,  or 
reddish,  to  blue — but  one  could  have  wished  for  a  larger 
number  of  instances.  At  present  we  can  only  say 
that  whilst  change  of  brilliancy  in  the  case  of  stars  is  a 
common  occurrence,  change  of  colour  is  not  a  well-estab- 
lished fact. 

CHAPTER   X. 

MOVING  STARS. 

The  term  "  fixed  stars  "  is  a  familiar  one,  and  in  a 
certain  sense  it  is  the  expression  of  a  truth,  but  modern 
science  has  shown  that  the  term,  as  applied  to  the  stars, 
needs  to  be  employed  under  reserve,  for  a  great  many 
stars  are  not  "fixed."  I  am  not,  of  course,  alluding  to 
their  apparent  annual  or  diurnal  movements:  we  have 
considered  that  matter  in  a  previous  chapter,  and  I  hope 
the  reader  understands  by  this  time  (at  any  rate  generally) 
what  these  apparent  movements  are  and  how  they  arise. 
What  we  have  now  to  deal  with  is  actual  proper  motion, 
and  with  this  a  considerable  number  of  the  stars  are  en- 
dued. 

It  must  be  understood,  of  course,  that  though  the  an- 
cients divided  the  stars  into  two  classes — those  which 
were  stationary,  and  those  which  moved — they  knew 
nothing  of  the  stars  which  form  the  subject  of  this  chap- 
ter being  moving  stars.  The  objects  to  which  the  an- 
cients applied  the  designation  of  "wandering  stars"  were 
what  we  now  call  Planets,  or  Comets.  Indeed,  the  very 
word  "planet"  itself  is  derived  from  a  Greek  word  mean- 
ing "a  wanderer."  What  we  have  now  to  consider  are 
the  movements  of  certain  stars,  which  movements  are,  as 
a  rule,  very  small  in  amount,  and  proceed  very  slowly. 
Sir  John  Herschel's  statement  of  the  case  can  hardly  be 


68  THE  STORY  OF  THE  STARS. 

improved  on.  He  says  : — "  Motions  which  require  whole 
centuries  to  accumulate  before  they  produce  changes  of 
arrangement  such  as  the  naked  eye  can  detect,  though 
quite  sufficient  to  destroy  that  idea  of  mathematical  fixity 
which  precludes  speculation,  are  yet  too  trifling,  as  far  as 
practical  applications  go,  to  induce  a  change  of  language 
and  lead  us  to  speak  of  the  stars  in  common  parlance  as 
otherwise  than  tixed.  Small  as  they  are,  however,  as- 
tronomers once  assured  of  their  reality  have  not  been 
wanting  in  attempts  to  explain  and  reduce  them  to  gen- 
eral laws." 

What  the  expression  the  "  proper  motion  "  of  a  star 
means  or  involves  may  perhaps  be  best  understood  by 
some  such  illustration  as  the  following : — A  man  standing 
in  Trafalgar  Square  and  looking  down  Whitehall  may  at 
a  given  moment  see  in  the  direction  of  the  Houses  of  Par- 
liament an  omnibus,  a  cab,  and  a  van.  After  an  interval 
of  2  minutes  he  may  see  the  same  vehicles,  but  their  order 
may  be  first  the  van,  then  the  cab,  and  lastly  the  omnibus. 
This  may  imply  either — (i)  that  the  van  has  remained 
stationary,  the  omnibus  and  the  cab  having  moved  for- 
wards, the  omnibus  travelling  at  a  more  rapid  pace  than 
the  cab;  or  (2)  that  all  three  have  moved  somewhat,  but 
each  at  a  different  pace  ;  or  (3)  that  the  van  has  backed 
towards  Trafalgar  Square,  only  the  omnibus  and  the  cab 
going  forward.  If  such  a  condition  of  things  were  con- 
ceived to  be  transferred  to  the  heavens,  our  ideal  omnibus, 
cab,  and  van  being  transformed  into  stars,  we  should  have 
an  analogue  of  the  problem  which  the  astronomer  has  to 
solve  in  detecting  and  valuing  the  proper  motions  of  3 
neighbouring  stars,  or,  it  may  be,  of  only  2,  or  perhaps 
even  of  only  i,  of  such  stars.  Be  it  remembered,  too, 
that  in  the  illustration  I  have  given  it  may  well  happen 
that  the  Trafalgar  Square  spectator,  from  his  position 
astride  of  one  of  Landseer's  lions,  though  he  may  be  quite 


MOVING  STARS.  69 

sure  that  the  omnibus  and  the  cab  have  both  moved  for- 
wards, may  yet  be  totally  incapable  of  determining  whether 
their  movement  amounts  to  10  yards  or  50  yards,  because 
he  is  viewing  the  whole  proceeding  "  end  on,"  or,  in  as- 
tronomical language,  the  3  vehicles  are  nearly  in  his  "  line 
of  sight."  Things  would,  however,  present  quite  a  differ- 
ent aspect  to  a  second  spectator  standing,  say,  in  front  of 
the  Horse  Guards.  His  would  be  a  "  broadside  "  view  of 
the  several  vehicles;  and  whether  they  had  all  moved,  or, 
if  only  some  of  them,  then  which  of  them,  and  how  much 
had  each  moved,  would  be  points  upon  which  he  could 
pronounce  an  opinion  promptly  and  (let  us  hope)  accu- 
rately. 

The  above  simile  in  each  and  all  its  stages  and  as- 
pects may  be  taken  to  be  a  counterpart  of  the  problem 
presented  to  an  astronomer  called  upon  to  investigate 
stellar  proper  motions.  And  what  Fontenelle  once  said 
in  respect  of  the  star  known  as  Altair  in  the  constellation 
Aquila  is  in  keeping  with  the  illustration  which  I  have 
borrowed  from  what  may  be  seen  any  day  at  Trafalgar 
Square.  Said  Fontenelle  : — "  There  is  a  star  in  the  Eagle 
which,  if  all  things  continue  their  present  course,  will, 
after  the  lapse  of  a  great  number  of  ages,  have  to  the 
west  another  star  which  at  present  appears  to  the  east  of 
it."  *  Fontenelle's  remark  is  just  such  a  remark  as  my 
ideal  spectator  at  the  Horse  Guards  might  make  because 
of  his  enjoying  a  "  broadside  "  view  of  the  changes  in  the 
positions  of  the  vehicles  going  down  Whitehall.     But  the 

*  Referring  to  the  diagram  of  the  stars  in  Ursa  Major,  given  on 
p.  36  {ante),  it  may  be  noted  that  all  7  are  endued  with  proper  mo- 
tion ;  but  whilst  3,  -y.  5,  e,  ^  are  moving  one  way,  a  and  r?  are  moving 
the  opposite  way,  and  Fontenelle's  remark  (varied  as  necessary) 
finds  a  further  exemplification.  Various  examples  may  be  found  of 
stars  in  proximity  having  common  proper  motions  or,  as  Miss 
Gierke  words  it,  having  a  ' '  gregarious  tendency." 


70  THE  STORY  OF  THE  STARS. 

original  spectator  at  the  Nelson  Monument  has  also  his 
circumstances  reproduced  in  the  heavens  ;  for,  even  though 
in  the  case  of  any  given  star  no  indications,  or  but  slight 
indications,  of  lateral  change  of  place  can  be  detected,  yet 
such  star  may  nevertheless  be  endued  with  a  rapid  mo- 
tion of  either  approach  or  recession  v^^hich  can  be  found 
out  by  a  secondary  method.  Thanks  to  the  spectroscope 
and  the  ingenuity  of  modern  astronomers,  motions  of  ap- 
proach to  or  recession  from  the  earth  have  been  discov- 
ered in  the  case  of  certain  stars,  notwithstanding  that 
those  stars,  being  seen  "  end  on  "  {alias,  in  the  line  of 
sight),  seem  on  mere  visual  observation  to  be  practically 
stationary. 

But  I  am  anticipating  too  much.  The  fact  that  certain 
of  the  stars  are  endued  with  a  proper  motion  of  their  own 
was  first  ascertained  in  1718  by  the  English  astronomer 
Halley.  By  comparing  the  positions  of  Sirius,  Arcturus, 
and  Aldebaran,  as  laid  down  in  the  most  ancient  cata- 
logues, with  the  positions  determined  by  himself  in  171 7, 
he  found,  after  making  every  allowance  for  the  effects  of 
precession  and  the  variation  in  the  obliquity  of  the  ecliptic, 
that  these  stars  seemed  to  have  got  out  of  place  to  the 
extent  in  each  case  of  more  than  \° ,  a.  displacement  too 
considerable  to  be  ascribable  to  errors  of  observation  or 
errors  of  copying.  In  the  case  of  Aldebaran  it  was  further 
found  that  that  star  had  undergone  at  Athens  in  509  A.  D. 
an  occultation  by  the  Moon  which  could  not  have  taken 
place  if  the  star  had  occupied  1400  years  ago  the  same 
or  nearly  the  same  place  that  it  occupies  at  the  present 
time.  The  utmost  that  Halley  could  do  was  to  surmise 
that  the  stars  in  question  were  affected  by  proper  motion, 
because  in  those  days  no  long-continued  series  of  observa- 
tions of  places  taken  by  exact  instruments  were  in  exist- 
ence. Such  observations,  however,  soon  began  to  accu- 
mulate as  the   1 8th  century  rolled  on,  and  accordingly  in 


MOVING  STARS.  7 1 

^738  James  Cassini  was  able  to  say  with  some  confidence 
that  Arcturus  had  undergone  a  displacement  of  5'  in  a 
century  and  a  half,  whilst  the  neighbouring  star  r]  Bootis 
had  been  exempt  from  such  displacement.  Inasmuch, 
however,  as  precise  and  exact  instrumental  observations 
of  star  places  can  only  be  said  to  date  from  1760  (being 
the  epoch  of  Bradley's  Catalogue  of  important  stars)  and 
as  that  was  only  a  century  and  a  quarter  ago  it  is  evidently 
clear  that  the  study  of  stellar  proper  motions  must  be  re- 
garded as  a  branch  of  the  science  which  is  still  in  its  in- 
fancy, especially  seeing  that  in  the  case  of  the  star  having 
the  largest  known  proper  motion  (1830  Groombridge  Ursae 
Majoris),  the  amount  is  only  y",  and  that  only  in  the  case 
of  about  a  dozen  stars  does  the  amount  exceed  3".  It  was 
to  a  fact  such  as  this  that  Sir  J.  Herschel  alluded  in  the 
paragraph  quoted  on  a  previous  page,  when  he  spoke  of 
"  motions  which  require  whole  centuries  to  accumulate 
before  they  produce  changes  of  arrangement  such  as  the 
naked  eye  can  detect." 

Year  by  year  is  adding  to  the  number  of  the  observa- 
tions, which  by  their  exactitude  enable  us  to  detect  proofs 
of  proper  motion  when  those  observations  are  placed  in 
juxtaposition  with  observations  of  the  same  stars  made  in 
the  earlier  part  of  the  present  century,  say  between  1800 
and  1830.  The  materials  already  available  seem  to  point 
to  the  fact  that  the  proper  motions  of  the  brighter  stars 
are,  as  a  rule,  greater  than  those  of  the  fainter  stars.  The 
average  proper  motions  of  the  ist  magnitude  stars  known 
to  possess  proper  motions  has  been  set  down  ac  J"  annu- 
ally, whilst  the  average  displacement  of  the  6th  magni- 
tude stars  known  to  be  affected  amounts  to  no  more 
than  ^Y- 

This  law,  if  law  it  may  be  properly  called,  is  subject 
to  exceptions,  for  there  are  some  small  stars,  such  as  1830 
Groombridge  Ursae  Majoris,  9352  Lac.  Piscis  Australis,  61 


72         THE  STORY  OF  THE  STARS. 

Cygni,  21 185  Lalande  Ursas  Majoris,  and  21258  Lalande, 
w^hich  have  very  considerable  proper  motions. 

The  reader  who  has  followed  attentively  the  Trafalgar 
Square  illustration  will  have  no  difficulty  in  understanding 
the  statement  that  a  knowledge  of  a  star's  proper  motion 
conveys  very  little  information  as  to  the  said  star's  real 
motion  reckoned  in  miles  per  second.  When  we  say  that 
a  star's  proper  motion  amounts  to  4"  a  year  (which  is 
about  6^'  in  a  century),  the  record  is  simply  that  the  star's 
apparent  lateral  displacement  is  so  much  in  such  a  length 
■of  time  along  a  line  assumed  to  run  at  right  angles  to  the 
observer's  line  of  sight.  But  the  true  direction  may  not 
be  at  right  angles  as  aforesaid ;  it  may  be  in  a  path  which 
the  observer  may  only  see  foreshortened.  Or,  in  an  ex- 
treme case,  if  the  motion  takes  place  directly  in  the  line  of 
sight  so  that  the  star  is  moving  straight  towards  us,  or 
from  us,  it  may  be  in  rapid  motion  and  yet  visually  seem 
to  have  no  motion  at  all ;  that  is,  to  be  undergoing  no 
■change  of  apparent  place  which  can  be  detected  by  com- 
paring observations  taken  at  different  times. 

Whilst  it  cannot  be  said  that  we  know  much  about  the 
actual  motions  of  many  of  the  stars,  yet  we  do  know 
something.  The  spectroscope  furnishes  us  with  some 
ciue,  the  basis  of  which  is  a  principle  of  physics  first  enun- 
ciated by  Uoppler  in  1842.  This  principle  may  be  thus 
•defined  : — "  When  the  distance  between  us  and  a  body 
which  IS  emitting  regular  vibrations  either  of  sound  or 
light  is  decreasing,  then  the  number  of  pulsations  received 
by  us  in  each  second  is  increased,  and  the  length  of  the 
waves  is  correspondingly  diminished."  In  the  case  sup- 
posed the  musical  pitch  rises,  and  in  the  same  way  the 
refrangibiiity  of  a  wave  of  light  which  depends  upon  its 
wave  length  is  increased  so  that  it  will  fall  nearer  the  vio- 
let end  of  the  spectrum.  A  practical  illustration  of  this 
principle  may  often  be  had  by  a  person  standing  on  the 


MOVING  STARS.  73 

platform  of  a  railway  station  through  which  a  fast  train  is 
passing  at  a  high  rate  of  speed,  whistling  continuously  as 
it  passes.  It  will  be  noticed  in  such  a  case  that  the  pitch 
of  the  whistle  continuously  varies  as  the  train  approaches 
the  spectator,  whilst  it  goes  on  continually  varying,  but  in 
the  opposite  direction,  after  it  has  passed  him  and  the  dis- 
tance gradually  augments.  Whatever  was  the  pitch,  say,  at 
200  yards,  before  the  engine  came  up  to  the  platform,  the 
pitch  will  be  the  same  at  200  yards  in  the  opposite  direc- 
tion after  the  engine  has  passed  the  platform. 

Huggins,  in  1868,  thought  to  apply  the  foregoing  prin- 
ciple by  spectroscopic  observations  on  certain  stars  with  a 
view  of  seeing  whether  a  particular  line  in  a  spectrum  un- 
derwent after  an  interval  any  displacement  from  its  nor- 
mal position  towards  either  end  of  the  spectrum.  If  in 
any  given  case  there  was  a  displacement  towards  the  red 
end  of  the  spectrum,  the  conclusion  would  have  to  be  that 
the  star  was  receding  from  the  earth  :  if,  on  the  other 
hand,  the  displacement  was  towards  the  violet  end  of  the 
spectrum,  the  conclusion  would  have  to  be  that  the  star 
was  approaching  the  earth.  A  general  deduction  to  be 
drawn  from  the  observations  of  Huggins  and  of  others 
who  have  worked  in  the  same  field,  seems  to  be  that  there 
are  several  dozen  prominent  stars  in  motion  at  speeds 
varying  from  2  to  50  miles  a  second. 

When  astronomers  once  came  to  recognise  the  fact 
that  certain  stars  were  in  motion  it  naturally  followed  that 
there  was  a  desire  to  ascertain  whether  any  particular 
consequences,  and  if  so  what  consequences,  were  involved 
in  the  discovery.  Sir  W.  Herschel  in  1783  began  by  try- 
ing to  classify  the  proper  motions  of  the  stars,  so  far  as 
known  to  him  at  that  epoch.  Having  done  this  and  find- 
ing evident  signs  that  they  converged  towards  a  point  in 
the  Constellation  Hercules,  he  was  led  to  conclude  that 
the  Solar  System  as  a  whole  was  moving  towards  a  point 


74  THE  STORY  OF  THE  STARS. 

in  the  Celestial  Sphere  not  far  from  the  star  X  Herculis. 
The  principle  involved  has  been  thus  defined  by  Professor 
Young : — "  On  the  whole,  the  stars  appear  to  drift  bodily 
in  a  direction  opposite  to  the  sun's  real  motion.  Those  in 
that  quarter  of  the  sky  which  we  are  approaching  open 
out  from  each  other,  and  those  in  the  rear  close  up  be- 
hind us.  The  motions  of  the  individual  stars  lie  in  all 
possible  directions,  but  when  we  deal  with  them  by  thou- 
sands, the  individual  is  lost  in  the  general,  and  the  pre- 
vailing drift  appears." 

The  effect  here  stated  by  Young  may  be  seen,  and 
being  seen,  may  be  easily  realised,  by  walking  through  a 
field  dotted  over  with  units  of  any  kind,  such  as  sheaves 
of  corn  put  up  in  shocks,  or  haycocks,  or  any  similar 
aggregations  of  produce.  As  the  pedestrian  approaches 
a  row  of  such  things,  the  row  which  at  a  distance  seemed 
almost  continuous  will  be  found  on  nearing  it  to  have  its 
units  separated  by  several  feet  or  yards  of  distance :  as  he 
passes  forwards  across  the  field  the  first  and  subsequent 
rows  will  gradually  seem  to  close  up  behind  him  into  a 
more  or  less  compact  mass. 

Sir  W.  Herschel's  endeavours  to  find  out  the  "  apex  "\ 
of  the  sun's  way  (as  it  is  called)  have  been  followed  up  by 
other  astronomers  since,  and  about  20  different  determina- 
tions are  now  available.  There  is  a  remarkable  general 
accord  between  them  all.  Perhaps  on  the  whole  the 
most  trustworthy  because  it  is  based  upon  a  very  large 
number  of  stars  is  L.  Struve's,  He  has  found  the  point 
of  convergence  to  be  situated  in  R.  A.  i8h.  13m.;  and 
Decl.  4-  27°.  Huggins,  by  spectroscopic  observations  of 
an  ingenious  character,  has  confirmed  the  general  conclu- 
sions thus  stated. 

A  skilful  and  careful  German  astronomer,  named  Mad- 
ler,  at  that  time  employed  at  the  Observatory  of  Dorpat 
in  Russia,  put  forth,  in  1846,  an  idea  that  there  exists 


TEMPORARY  STARS.  75 

some  central  point  in  the  universe  around  which  the  sun, 
with  its  bevy  of  planets  and  comets,  revolves  in  the  course 
of  millions  of  years  ;  and  he  suggested  that  such  centre  is 
situate  in  the  direction  of  Alcyone,  one  of  the  Pleiades. 
It  is  difficult  to  pronounce  dogmatically  for  or  against 
jthis  idea  (which,  by  the  way,  was  rather  a  revival  of  a 
theory  put  forth  by  Wright  in  1750  than  Madler's  own), 
but  Grant's  remarks  may  be  considered  to  meet  the  case : 
— "  It  is  manifest  that  all  such  speculations  are  far  in  ad- 
vance of  practical  astronomy,  and  therefore  they  must  be 
regarded  as  premature." 

CHAPTER   XI. 

TEMPORARY    STARS. 

Historians  of  various  dates  and  nationalities  tell  us 
that  from  time  to  time  stars  have  blazed  forth  in  the  heav- 
ens in  places  where  no  stars  had  ever  been  seen  before, 
and  that  after  an  existence  of,  it  may  be,  a  few  weeks  or 
months,  such  stars  have  faded  away  and  been  no  more 
seen.  It  was  at  one  time  considered  that  the  authors  of 
these  statements  had  been  drawing  upon  their  imagination 
for  their  facts,  but  the  bulk  of  what  has  been  handed  down 
to  us  are  well  founded.  About  12  stars  in  all  are  recog- 
nised by  astronomers  under  the  designation  of  "  temporary 
stars."  They  severally  appeared  as  follows  :  134  B.  C,  329 
A.  D.,  1572,  1600,  1604,  1670,  1848  (A^^7^«  Ophiuchi),  i860 
(T  Scorpii),  1866  (T  Coronse),  1876  {Nova  Cygni),  1885 
(^Nova  Andromedas),  and  1892  {Nova  Aurigcc).*  The  chief 
difficulty  in  regard  to  all  the  more  ancient  cases  has  been 

*  Since  this  chapter  was  written  have  appeared  :  Nova  Carinas 
and  Nova  Centauri,  1895  ;  Nova  Sagittarii,  1898 ;  Nova  Aquillas, 
1899  ;  and  Nova  Persei,  1901.  The  latter  reached  almost  the  bright- 
ness of  Sirius,  February  24,  and  in  some  respects  was  the  most  re- 
markable astronomical  phenomena  of  recent  years. 


76  THE  STORY  OF  THE  STARS. 

to  determine  how  far  the  celestial  objects  thus  recorded  to 
have  burst  forth  were  in  any  true  sense  stars,  or  whether 
they  were  comets  or  mere  meteors.  The  records  which 
we  have  are  of  very  diverse  origin,  and  some  of  them 
2000  years  old,  handed  down  to  us  from  times  when  the 
scientific  precision  and  verbal  accuracy  of  modern  writing 
and  speech  were  unknown.  The  fact  that  the  ancient 
Greeks  were  a  dreamy  people,  the  Romans  callous  to  sci- 
ence altogether,  and  the  Chinese  "  flowery  "  as  nowadays, 
renders  it  extremely  difficult  for  us  to  sift  the  wheat  from 
the  chaff,  and  to  preciser,  as  the  French  say,  any  given 
statement.  For  instance,  what  is  one  to  make  out  of  the 
following  Chinese  account  of  something  seen  in  A.  D. 
173- — "On  Dec.  loth  a  star  appeared  between  a  and /3 
Centauri,  and  remained  visible  for  7  or  8  months ,  it  was 
like  a  large  bamboo  mat  (!),  and  displayed  5  different 
colours."  Were  it  not  for  the  fact  that  on  several  occa- 
sions during  the  present  century  new  stars  have  burst 
forth,  have  shone  for  a  while,  and  have  then  either  disap- 
peared absolutely  or  dwindled  almost  to  invisibility,  we 
should  often  have  to  be  sceptical  as  to  the  tales  told  us  by 
many  ancient  chroniclers. 

Our  sources  of  information  are  twofold — European  and 
Chinese.  The  former  are  generally  very  vague  as  to  dates 
and  places;  the  latter  much  more  "understandable," 
though  both  dates  and  places  are  often  expressed  in  a 
very  peculiar  fashion.  The  Chinese  observations  have 
the  great  merit  that  they  are  continuous  through  many 
centuries,  and  are  expressed  in  language  of  very  uniform 
style ;  so  that  once  get  an  insight  into  the  style,  and  a 
European  astronomer  may  feel  sure  that  he  can  interpret 
with  tolerable  accuracy  the  entire  series,  and  this  is  what 
has  been  done.  The  first  workers  in  this  field  were  cer- 
tain French  Jesuit  missionaries,  named  Couplet,  Gaubil, 
and  De  Mailla,  who  lived  for  a  while  at  Pekin  some  1 50 


TEMPORARY  STARS.  77 

years  ago.  They  made  and  brought  to  France  copies  of 
various  Chinese  annals,  which  somehow  or  other  they  got 
hold  of  at  Pekin.  De  Mailla's  manuscripts  were  pub- 
lished at  Paris  about  loo  years  ago,  but  those  of  Couplet 
and  Gaubil  still  remain,  I  believe,  unpublished.  A  very 
industrious  Frenchman  named  Pingre  worked  up  all  these 
materials  in  a  book  on  comets  which  he  published  in 
1784,  whilst  another  Frenchman  named  Biot  in  1846  gave 
to  the  world  a  further  series  of  observations.  By  far  the 
most  complete  and  accurate,  however,  of  all  the  existing 
versions  of  the  Chinese  astronomical  records  is  the  late 
John  Williams's  "Observations  of  Comets  from  B.C.  611 
to  A.  D.  1640,"  which  appeared  in  1871. 

All  this  is  a  digression  from  the  subject  which  I  wanted 
to  start  with,  but  it  is  a  digression  which  seemed  neces- 
sary under  the  circumstances  of  the  case. 

The  earliest  "  new  "  star  appears  to  have  been  one  ob- 
served by  the  Greek  astronomer  Hipparchus,  and  a  tradi- 
tion, fathered  by  Pliny,  has  always  suggested  that  it  was 
the  appearance  of  this  star  which  prompted  Hipparchus 
to  compile  his,  the  first  catalogue  of  stars.  This  tradition 
was  long  regarded  as  a  myth,  but  as  a  new  star  in  Scorpio 
is  recorded  by  the  Chinese  to  have  been  seen  in  134  B.C., 
a  few  years  before  the  date  commonly  assigned  to  Hippar- 
chus's  Catalogue,  there  seems  now  no  sufficient  reason  for 
rejecting  the  tradition  above  referred  to.  Passing  over 
new  stars  asserted  to  have  appeared  in  945  A.  D.  and  1264 
A.  D.,  the  authenticity  of  which  is  gravely  doubtful  (the 
accounts  probably  referring  to  the  great  comets  of  those 
years),  we  come  to  the  year  1572.  In  that  year  there  was 
a  celebrated  new  star  with  which  Tycho  Brahe's  name  is 
often  linked,  because  he  left  behind  him  a  particularly  full 
account  of  it.  It  was  v'isible  for  17  months  from  Novem- 
ber, 1572,  to  March,  1574.  Brighter  than  Sirius,  it  rivalled 
Venus.     It  changed  colour  from  white  to  yellow  and  red 


78         THE  STORY  OF  THE  STARS. 

and  then  back  again  to  white,  and  remained  stationary  all 
the  while  that  it  was  visible.  D' Arrest  pointed  out  in  1864 
that  within  i'  of  arc  of  the  place  assigned  by  Argelander 
to  Tycho's  star  there  exists  a  small  star,  which  Hind  and 
Plummer  found  in  1873  ^o  be  certainly  variable  in  its 
light.  The  position  for  1890  of  Tycho's  star  is  R,  A.,  oh. 
1 8m.  40s.;  Decl.  4-  63°  32'.3.  Amateurs  possessed  of 
telescopes,  say  of  3  inches  aperture,  might  usefully  em- 
ploy their  time  in  finding  and  watching  this  supposed 
Tycho  star.  It  follows  a  certain  9th  mag.  star  at  a  dis- 
tance of  21. 6s.,  and  is  10' 4"  to  the  S.  This  9th  mag. 
star  may  itself  be  identified  by  reason  of  the  fact  that  it 
follows  a  star  known  as  Flamsteed's  10  Cassiopeise  (mag. 
6)  at  a  distance  of  17m.  12s.,  and  is  6.4'  to  the  N.  of  it. 

In  1604  and  in  1670  temporary  stars  of  considerable 
brilliancy  became  visible.  The  star  of  1604  appeared  in 
Ophiuchus,  and  grew  to  be  nearly  as  bright  as  Venus, 
lasting  12  months  or  longer.  The  star  of  1670,  often 
called  "  Anthelm's  star,"  appeared  in  Cygnus,  and  reached 
the  brightness  of  a  star  of  the  3rd  mag.  It  lasted  alto- 
gether about  2  years,  but  faded  away  and  then  bright- 
ened up  again  more  than  once  before  its  final  disap- 
pearance. 

In  April,  1848,  a  new  star  of  the  5th  mag.  was  seen  in 
Ophiuchus  by  Hind.  It  eventually  rose  to  the  4th  mag., 
and  then  faded  away  and  became  very  small,  but  has 
never  entirely  disappeared.  This  star  is  now  ranked  as  a 
recognised  variable,  but  it  seems  not  to  have  received 
much  notice  of  late  years. 

In  1866  a  very  remarkable  transformation  took  place 
in  the  case  of  a  star  which  had  been  previously  recorded 
in  1855  by  Argelander  as  being  of  the  9th  or  loth  mag. 
Birmingham  at  Tuam,  on  May  12,  1866,  found  the  star 
shining  as  of  the  second  mag.  Combining  the  testimony 
of  Birmingham  with  that  of  Schmidt  of  Athens,  it  would 


TEMPORARY  STARS.  79 

seem  that  this  star  brightened  up  from  the  4th  to  the  2nd 
mag.  in  about  3  hours  on  the  evening  of  May  12.  It 
soon  began  to  lose  light,  and  after  diminishing  to  below 
mag.  9  it  rose  to  7i  in  September,  and  remained  at  that 
for  the  rest  of  the  year.  This  star  also  is  now  treated  as 
a  recognised  variable,  though  we  have  gained  very  little 
additional  knowledge  respecting  it. 

In  November,  1876,  after  several  days  of  pronounced 
bad  weather,  Schmidt  at  Athens  observed  on  the  24th  a 
new  star  of  the  3rd  mag,,  yellow  in  colour.  By  the  begin- 
ning of  December  it  had  sunk  to  the  5th  mag.,  and  by  the 
end  of  December  to  the  7th  mag.,  and  now  it  seems  to 
have  disappeared  altogether. 

In  August,  1885,  a  new  star  burst  out  in,  or  in  front  of, 
the  Great  Nebula  in  Andromeda.  Though  it  only  reached 
the  6th  mag.,  yet,  owing  to  the  large  number  of  telescopes 
and  spectroscopes  brought  to  bear  on  it,  this  nova  has  a 
considerable  and  very  interesting  history  attached  to  it. 

One  moral  to  be  drawn  from  this  is  that  amateur 
observers  need  not  fancy  that  there  is  no  work  for 
them  to  do  in  Astronomy.  Respecting  this  star,  I 
Iwill  here  state  historically  what  seems  to  have  hap- 
Ipened.  The  Great  Nebula  in  Andromeda  is  one  of  the 
largest  and  most  important  of  the  known  nebulae,  as  we 
shall  see  when  v/e  come  to  speak  of  that  class  of  celestial 
objects.  It  ordinarily  offers  the  appearance  of  an  exten- 
sive and  dense  oval  mass  of  luminous  haze.  It  so  pre- 
sented itself  to  various  observers  during  the  first  half  of 
August,  1885.  Priority  in  noticing  it  to  be  otherwise — 
that  is,  as  having  a  star  in  or  on  it — seems  to  rest  either 
with  the  late  Mr.  Isaac  Ward,  of  Belfast,  or  with  a  Hun- 
garian lady,  the  Baroness  de  Podmaniczky,  who  on 
August  22  had  staying  with  her  at  her  husband's  house 
"^  professional  astronomer,  Dr.  De  Kovesligethy.  There 
was  a  telescope   of   3^  inches   aperture    in   the    house. 


So  THE  STORY  OF  THE  STARS. 

Hostess  and  guest  several  times  made  use  of  this 
telescope,  and  on  August  22  the  baroness  remarked  to 
the  doctor  that  she  saw  a  little  star  in  the  nebula,  a  state- 
ment which  the  visitor  confirmed.  Yet  the  phenomenon 
was  so  faint  that  both  believed  the  full  moon  was  the  in- 
direct cause,  the  moonlight  overshadowing  the  fainter 
portions  of  the  nebula,  and  permitting  only  of  the  visibil- 
ity of  the  bright  centre.  It  was  not  till  more  than  a  week 
after  the  above  date  that  the  existence  of  the  new  star 
was  generally  recognised,  though  there  is  evidence  to 
show  that  some  days  previously  to  August  22  the  nebula 
as  a  nebula  had  exhibited  unwonted  brightness.  To  none, 
however,  of  the  observers  who  noted  this  fact  does  it 
appear  that  the  thought  presented  itself  that  they  were 
gazing  on  a  stellar  object.  At  its  brightest  this  new  star 
seems  to  have  reached  the  6th  magnitude,  and  there  is 
reason  to  suppose  that  when  Mr.  Ward  and  the  Baroness 
de  Podmaniczky  saw  the  star  it  was  rising  to,  but  had  not 
reached,  its  maximum  brilliancy.  The  date  of  this  may 
perhaps  be  put  at  August  31.  The  star  then  rapidly  de- 
clined in  lustre  until  the  end  of  September,  when  it  stood 
at  about  the  loth  magnitude.  It  then  further  diminished 
until  it  became  merged  in  the  nebula  itself,  or  rather  until 
its  luminosity  became  lost  in  the  luminosity  of  the  nebula. 
An  interesting  question  arose  as  to  what  were  the  rela- 
tions, if  any,  between  the  new  star  and  the  nebula.  A 
very  competent  French  astronomer  named  Trouvelot  sug- 
gested the  following  reasons  for  concluding  that  there 
was  no  physical  connection  between  the  star  and  the  neb- 
ula. There  are  a  multitude  of  small  stars  visually  scat- 
tered all  over  the  nebula.  Trouvelot  considers  these  to 
belong  to  the  Milky  Way,  of  which  he  traces  an  extension 
beyond  the  nebula,  since  they  increase  in  number  as  the 
Milky  Way  is  approached.  They  are  likewise  perfectly 
€harp  and  well-defined,  which  they  would  not  be  if  they 


TEMPORARY  STARS.  8 1 

were  either  in  the  nebula  or  behind  it.  He  concludes, 
therefore,  that  the  nebula  lies  behind  the  Milky  Way. 
The  well-defined  appearance  of  the  new  star,  and  of  a 
small  star  near  it,  which  he  thought  was  also  a  new  one, 
seemed  to  prove  that  they  were  both  in  front  of  the  nebula, 
and  were  associated  with  the  Milky  Way  rather  than  with 
the  nebula.  These  surmises,  it  will  be  observed,  throw 
no  light  upon  the  question  why  this  new  star  should  sud- 
denly have  blazed  forth  and  as  suddenly  have  faded  away. 
I  must,  however,  add  my  testimony  to  Trouvelot's  so  far 
as  to  say  that  when  I  saw  the  new  star  myself  on  Sep- 
tember 3,  in  a  6-inch  refractor,  I  could  not  refrain  from 
entering  in  my  note-book  the  thought  that  "  the  star  had 
nothing  to  do  with  the  nebula." 

On  December  13,  1885,  Mr.  J.  E.  Gore  in  Ireland  no- 
ticed a  new  star  of  the  6th  magnitude,  reddish  in  colour, 
situated  some  20'  following  x^  Orionis.  It  was  found  to 
have  a  beautiful  banded  spectrum  of  Secchi's  Type  III. 
Six  months  later  it  had  diminished  to  below  the  12th  mag- 
nitude. It  afterwards  increased  again,  and  is  now  recog- 
nised as  a  variable  going  through  all  its  changes  of  mag- 
nitude in  about  12  months.  Why  the  sudden  and  special 
increase  of  its  light  in  December,  1885,  cannot  be  sur- 
mised. 

There  yet  remains  another  new  or  temporary  star  for 
mention,  the  history  of  which  is  extremely  interesting.  On 
February  i,  1892,  an  anonymous  postcard  was  received  by 
Dr.  Copeland,  the  director  of  the  Royal  Observatory  at 
Edinburgh,  to  the  effect  that  a  new  star  of  about  the  5th 
magnitude  had  become  visible  in  the  constellation  Auriga 
not  far  from  the  star  x-  It  subsequently  transpired  that 
the  postcard  had  emanated  from  a  certain  Dr.  Anderson, 
an  amateur  living  in  Edinburgh,  who  had  discovered  the 
star  by  the  joint  use  of  a  small  pocket  telescope  and  Mc- 
Clure's  edition  of  Klein's  "  Star  Atlas."     The  history  of 


82  THE  STORY  OF  THE  STARS. 

this  star  during  the  weeks  immediately  preceding  its  dis- 
covery by  Dr.  Anderson  became  known  in  a  very  curious 
way.  Professor  Pickering  of  Harvard  College,  U.  S.,  had 
recently  conceived  the  idea  of  "  patrolling  the  heavens  " 
every  fine  night  by  means  of  a  small  photographic  transit 
instrument  which  would  automatically  sweep  the  meridian 
in  a  series  of  steps  of  sufficient  exposure  to  photograph 
6th  magnitude  stars,  at  intervals  corresponding  to  the 
equatorial  breadth  of  the  field.  The  scheme  was  well 
adapted  for  the  detection  of  strange  objects  brighter  than 
6th  magnitude  stars,  and  so  it  resulted  that  Anderson's 
star  was  found  on  13  photographs  taken  between  Decem- 
ber 10,  1 89 1,  and  January  20,  1892.  As  it  appeared  on 
all  these,  which  embraced  stars  down  to  the  9th  magni- 
tude, but  was  not  to  be  found  on  the  photograph  of  De- 
cember 8th,  the  presumption  is  that  the  new  star  bright- 
ened up  from  below  the  9th  magnitude  between  December 
8th  and  December  loth.  After  remaining  at  about  the 
4th  or  5th  magnitude  till  the  end  of  February,  it  dimin- 
ished somewhat  rapidly  in  brightness,  and  by  the  end  of 
March  had  fallen  to  below  the  I2lh  magnitude.  Observa- 
tions were  continued  at  the  Lick  Observ^atory  in  California 
till  April  26th,  when  bad  weather  supervened.  It  was 
then  of  the  i6th  magnitude,  so  that  it  may  be  said  to  have 
practically  disappeared.  In  August,  however,  it  had 
brightened  up  again  to  above  the  loth  magnitude,  finally 
subsiding  to  about  the  12th  magnitude. 

I  have  dwelt  somewhat  fully  on  the  so-called  "tem- 
porary "  stars,  because  the  subject  is  one  which  seems  to 
open  up  opportunities  of  scientific  usefulness  to  the  class 
of  persons  under  whose  notice  this  volume  is  likely  to  fall 
— amateurs  possessed  of  small  telescopes,  or  with  no  tele- 
scopes at  all,  but  with  many  open-air  opportunities  of 
becoming  familiar  with  the  aspect  of  the  heavens. 

It  may  have  been  inferred  from  various  remarks  made 


VARIABLE   STARS.  S$ 

in  this  cliapter  that  temporary  stars,  and  variable  stars, 
which  will  form  the  subject  of  the  next  chapter,  are  so 
closely  associated  as  almost  to  imply  that  all  temporary 
stars  are  merely  variables  of  long  and  irregular  periods. 
There  is  much  to  support  this  idea,  as  also  the  correlative 
idea  that  many  of  the  "missing"  stars  are  also  variables 
not  yet  recognised  to  be  such.  But  Kirkwood,  an  ex- 
perienced and  thoughtful  American  observer,  considers 
that  the  theory  that  temporary  stars  are  long-period  vari- 
ables is  unsound  :  that  the  suddenness  of  their  apparition, 
the  short  duration  of  their  maximum  brightness,  and  the 
great  length  of  their  periods,  if  they  are  really  periodic,  are 
reasons  for  regarding  them  as  distinct  in  their  nature  from 
the  variable  stars  properly  so-called.  It  is  worthy  of 
notice  that  there  is  no  known  instance  of  a  new  star 
appearing  and  remaining  permanently  visible. 


CHAPTER    XII. 

VARIABLE   STARS. 

A  LISTLESS  observer  of  the  stars  will  regard  them  as 
always  preserving  their  brilliancy,  be  it  much  or  little,  un- 
changed, but  such  is  not  the  case  with  all  of  them  ;  a  cer- 
tain number  vary  from  time  to  time  in  their  Jight,  and  are 
therefore  called  "  variable  "  stars.  The  number  of  those 
of  which  it  may  be  said  with  certainty  that  they  undergo 
periodical  changes  of  brilliancy  amounts  to  nearly  300  ; 
but  it  is  probable  that  as  many  again  may  be  regarded  as 
possibly  subject  to  fluctuations  of  light.  In  the  absence 
of  absolute  standards  for  comparison,  the  systematic  study 
of  variable  stars  is  a  matter  involving  much  patience  on 
the  part  of  the  observer  and  much  refinement  in  his  pro- 
cedure.    Were  the  number  of  observers  endowed  with 


84  THE  STORY  OF  THE  STARS. 

the  requisite  patience  and  experience  much  increased, 
there  is  no  doubt  that  large  additions  would  soon  be  made 
to  our  lists  of  variable  stars.  This  department  of  astrono- 
my is  entirely  modern,  for  the  ancients  have  left  us  merely 
a  few  vague  statements  of  stars  having  disappeared,  and 
we  can  seldom  determine  with  adequate  precision  the 
places  occupied  by  them. 

Professor  Young  has  made  some  remarks  on  the 
method  of  observation  to  be  resorted  to  in  the  case  of 
variable  stars,  which  it  may  be  useful  to  quote  here.  He 
says  : — "  There  is  no  better  way  than  that  of  comparing 
the  star  by  the  eye,  or  with  the  help  of  an  opera-glass, 
with  surrounding  stars  of  about  the  same  brightness  at 
the  time  when  its  light  is  near  the  maximum  or  minimum  ; 
noting  to  which  of  them  it  is  just  equal  at  that  moment, 
and  also  those  which  are  a  shade  brighter  or  fainter.  It 
is  possible  for  an  amateur  to  do  really  valuable  work  in 
this  way,  by  putting  himself  in  relation  with  some  ob- 
servatory which  is  interested  in  the  subject.  The  observa- 
tions themselves  require  so  much  time  that  it  is  difficult 
for  the  working  force  in  a  regular  observatory  to  attend 
to  the  matter  properly,  and  outside  assistance  is  heartily 
welcomed  in  gathering  the  needed  facts.  The  observa- 
tions themselves  are  not  specially  difficult,  require  no 
very  great  labour  or  mathematical  skill  in  their  reduc- 
tion, and,  as  has  been  said,  can  be  made  without  instru- 
ments ;  but  they  require  patience,  assiduity,  and  a  keen 
eye." 

One  of  the  most  celebrated  of  the  periodical  stars  is 
o  Ceti,  otherwise  known  as  Mira  (the  '*  wonderful  "  star), 
which  latter  name  has  been  given  to  it  precisely  because 
it  undergoes  such  remarkable  changes.  Its  period  is 
33id.  8h. ;  that  is  to  say,  it  goes  through  its  changes  12 
times  in  about  1 1  years.  At  its  maximum  brightness  it 
sometimes  rises  to  the  2nd  mag.,  remaining  thereat  for 


VARIABLE  STARS.  85 

about  a  fortnight;  it  then  diminishes  during  about  3 
months,  becomes  invisible  except  in  large  telescopes  for  5 
months,  and  finally  requires  another  3  months  to  regain 
its  pristine  maximum  brilliancy.  These  may  be  taken  as 
average  intervals,  but  it  does  not  always  diminish  or  increase 
by  the  same  gradations ;  its  maximum  brightness  is  not 
always  the  same,  nor  are  the  intervals  of  time  between 
maximum  and  maximum  always  identical.  These  irregu- 
larities were  studied  very  carefully  by  Argelander,  who 
came  to  the  conclusion  that  the  period  of  33 id.  of  Mira 
itself  varies  in  about  88  of  such  periods,  with  the  result 
that  the  single  periods  gradually  lengthen  and  shorten 
alternately  to  the  extent  of  25  days  one  way  or  the  other. 
Moreover,  it  is  not  improbable  that  the  irregularities  in 
the  star's  maximum  brilliancy  are  also  periodical,  and  that 
at  every  nth  maximum  the  star  attains  to  a  greater  de- 
gree of  brilliancy  than  its  usual  maximum  brilliancy. 
This  supposition  would  explain  the  fact  that  whilst  the 
naked-eye  visibility  of  Mira  generally  extends  to  about  18 
weeks,  it  was  in  1859-60  so  observed  during  21  weeks, 
whilst  in  1868  the  term  was  but  12  weeks.  It  was  in  this 
year  that  Heis  noted  the  maximum  magnitude  to  be  only 
the  5th,  whilst  in  1888  it  attained  to  about  the  3rd  mag., 
and  therefore  of  course  remained  a  naked-eye  object  for 
a  much  longer  period.  The  discovery  of  the  variability  of 
this  star  dates  back  as  far  as  1596.  On  August  13  of  that 
year  David  Fabricius  noted  a  certain  star  in  Cetus  to  be 
of  the  3rd  magnitude.  In  the  following  October  he  failed 
to  find  it.  In  1603  Bayer,  in  preparing  his  "Star  Atlas," 
assigned  the  Greek  letter  o  to  a  star  in  Cetus  occupying 
the  spot  where  Fabricius's  star  had  disappeared.  He 
noted  it  to  be  of  the  4th  mag.,  but  being  either  ignorant 
of,  or  neglectful  of,  the  earlier  observations  of  Fabricius, 
he  lost  the  chance  of  being  able  to  claim  the  honour  of 
discovering  the  star's  variability.     The  spectrum  of  Mira 


S6  THE  STORY  OF  THE  STARS. 

is  a  remarkable  one  of  Secchi's  Ilird  Type,  in  which 
bright  Hnes  have  been  seen. 

Perhaps  Algol  (/3  Persei)  may  be  regarded  as,  after 
Mira  Ceti,  the  second  most  remarkable  variable  in  the 
heavens,  or,  at  any  rate,  in  the  Northern  hemisphere,  as  it 
is  second  also  in  point  of  date  of  discovery.  The  fact  of 
its  variability  was  noticed  by  Montanari  in  1669,  was  con- 
firmed by  Maraldi  in  1694,  and  investigated  half  a  century 
later  by  a  Saxon  farmer  named  Palitzch,  celebrated  for  his 
early  detection  of  Halley's  Comet  in  1758.  But  it  was 
Goodricke,  in  1782,  who  first  det'^rmined  in  full  detail  the 
changes  of  brilliancy  which  Algol  undergoes.  It  com- 
monly shines  as  a  star  of  mag.  2J ;  from  that  it  descends 
to  about  3|.  Pickering,  from  photometric  measures  at 
Harvard  College,  finds  that  the  star's  light  diminishes 
during  4h.  23m.  before  minimum.  When  the  minimum 
is  reached,  then  5h.  37m.  pass  before  the  star  regains  its 
normal  maximum.  It  remains  at  this  for  about  2d.  loh. 
The  most  rapid  changes  take  place  during  about  100 
minutes  before  and  100  minutes  after  the  epocK  of  mini- 
mum. Pickering  suggests  that  the  range  of  variability  is 
less  than  is  commonly  stated,  and  does  not  exceed  one 
whole  magnitude.  The  period  in  which  the  entire  series 
of  changes  take  place  is  about  2d.  2oh.  48m.,  and  is 
thought  by  Chandler  to  have  diminished  by  8s.  since 
Goodricke's  time ;  but  to  talk  about  8s.  in  such  a  connec- 
tion is  a  refinement  of  precision  which  savours  of  affec- 
tation. 

Another  naked-eye  variable  handy,  by  reason  of  its 
position  and  magnitude,  for  observers  in  the  Northern 
hemisphere  is  8  Cephei.  Its  period  is  5d.  8h.  47m.  count- 
ing from  minimum  to  minimum,  and  its  range  from  about 
mag.  3f  to  mag.  4|.  The  interval  between  maximum  and 
maximum  is  not  equally  divided  by  the  minimum  phase, 
for  it  takes  longer  for  the  star  to  pass  from  its  maxi- 


VARIABLE  STARS.  Sf 

mum  to  its  minimum  than  it  does  to  regain  its  maximum: 
after  a  minimum.  The  former  transformation  occupies- 
3d.  I9h.  but  the  latter  only  id.  I4h.  The  variability  of 
8  Cephei  was  discovered  by  Goodricke  in  1784,  and  the 
whole  period  is  put  at  5d.  8h.  48m. 

rj  Aquilae  and  /3  Lyrse  may  also  be  mentioned  as  short- 
period  variables,  which  on  that  account,  and  because  they 
are  visible  to  the  naked  eye,  are  specially  suitable  for  ob- 
servation by  amateurs  in  England. 

T]  Aquilas  varies  from  about  mag.  3^  to  mag.  4f  in  a 
period  of  about  yd.  4h.  14m.,  but  this  period  itself  seems 
variable.  The  star  is  yellow  in  colour  and  yields  a  spec- 
trum of  Secchi's  Ilnd  Type. 

/3  Lyras  is  remarkable  as  having  a  double  maximum 
and  a  double  minimum,  which  together  make  up  a  main 
period  of  I2d.  2ih.  47m.  The  variations  take  the  follow- 
ing form  : — Starting  from  a  maximum  when  the  star  is  of 
mag.  3J-,  it  descends  to  its  first  minimum  of  mag.  4 ;  it 
then  rises  to  the  same  maximum  as  before,  but  in  descend- 
ing to  the  next  minimum  it  goes  down  to  mag.  4^.  Arge- 
lander  ascertained  that  /3  Lyrae  resembles  Mira  Ceti  as 
regards  the  circumstances  of  its  period — in  other  words, 
that  its  period  is  itself  variable;  that  down  to  1840  the 
period  was  increasing,  but  that  after  1840  it  began  to  de- 
crease, and  was  decreasing  at  the  time  when  Argelander 
made  this  remark  in  1866.  Pickering  has  propounded  the 
idea  that  this  star  is  a  "  surface  of  revolution  "  or  a  sphe- 
roid in  form  and  differently  luminous  in  different  parts, 
and  that  the  epoch  of  minimum  light  represents  a  time 
when  the  darker  portion  at  one  of  the  ends  is  presented 
to  the  earth.  This  seems  to  be  one  of  those  far-fetched 
fancies  which  can  neither  be  proved  nor  disproved.  The 
variability  of  /3  Lyras  was  discovered  by  Goodricke  in 
1784. 

I  have  reserved  to  the  last  that  which  is  perhaps  the 


88  THE  STORY  OF  THE  STARS. 

most  remarkable,  as  certainly  it  is  the  most  erratic,  of  all 
the  prominent  variable  stars — r)  Argus.  Unfortunately  it 
is  not  visible  in  the  Northern  hemisphere.  Halley,  on  his 
return  from  St.  Helena,  as  far  back  as  1677,  frequently  ex- 
pressed doubts  as  to  the  constancy  of  the  light  of  the  stars 
in  Argo.  Though  he  seems  only  to  have  based  his  conclu- 
sions upon  Ptolemy's  statements  of  star  magnitudes,  yet 
these  w^ere  generally  so  accurate  that  when  discrepancies 
were  found  to  exist  between  modern  and  ancient  records 
the  idea  at  once  suggested  itself  that  there  had  been  actual 
■change  rather  than  mistakes  of  observation.  Halley,  in 
1677,  rated  i]  Argus  as  of  the  4th  magnitude.  In  1751 
La  Caille  noted  it  as  of  the  2nd  magnitude.  In  the  next 
half  century  it  diminished,  for  Burchell,  during  his  resi- 
dence and  travels  in  South  Africa,  between  181 1  and 
181 5,  saw  it  as  of  the  4th  magnitude.  Fallows,  in  1822, 
at  the  Cape,  and  Sir  T.  M.  Brisbane,  between  1822  and 
1826,  in  New  South  Wales,  saw  it  as  of  the  2nd  magni- 
tude. In  the  following  year,  that  is,  on  Feb.  i,  1827, 
Burchell,  then  at  St.  Paul's,  in  Brazil,  saw  it  as  of  the  ist 
magnitude,  and  almost  as  bright  as  a  Crucis ;  but  within 
a  year,  that  is,  by  Feb.  20,  1828,  it  had  decreased  to  the 
2nd  magnitude,  and  as  such  was  entered  by  M.  J.  John- 
son and  Taylor  in  their  respective  catalogues  between 
1829  and  1833.  Sir  John  Herschel,  who  started  observa- 
tions at  the  Cape  in  1834,  found  it  then  and  for  several 
years  afterwards  to  be  something  between  mags,  i  and  2 
but  nearer  2.  It  seems  to  have  remained  stationary,  or 
nearly  so,  for  well-nigh  3  years,  but  on  December  16, 
1837,  on  resuming  work  after  an  interval,  Sir  John  was 
startled  to  find  it  had  become  one  of  the  very  brightest 
stars  of  the  ist  magnitude,  excelling  all  belonging  to  that 
category  except  Sirius  and  Canopus.  Sir  John  Herschel's 
account  of  it  will  bear  quoting : — "  Its  light  was  nearly 
tripled.  ...  It  very  decidedly  surpassed  Procyon,  which 


VARIABLE  STARS.  89 

was  about  the  same  altitude,  and  was  far  superior  to  Al- 
debaran.  It  exceeded  a  Ononis,  and  the  only  star  (Sirius 
and  Canopus  excepted)  which  could  at  all  be  compared 
with  it  was  Rigel,  which  it  somewhat  surpassed.  From 
this  time  its  light  continued  to  increase.  On  December 
28  it  was  far  superior  to  Rigel  and  could  only  be  com- 
pared with  a  Centauri,  which  it  equalled,  having  the  ad- 
vantage of  altitude,  but  fell  somewhat  short  of  it  as  the 
altitudes  approached  equality.  The  maximum  of  bright- 
ness seems  to  have  been  obtained  [attained]  about  Janu- 
ary 2,  1838,  on  which  night  both  stars  being  high  and  the 
sky  clear  and  pure,  it  w-^s  judged  to  be  very  nearly 
matched  indeed  with  a  Centauri,  sometimes  the  one, 
sometimes  the  other,  being  judged  brighter,  but  on  the 
whole  a  was  considered  to  have  some  little  superiority. 
After  this  the  light  began  to  fade."  Sir  John  then  goes  on 
to  narrate  the  incidents  of  the  declension  of  the  star's  light. 
His  own  observations  ceased  in  April,  1838,  but  the  star 
even  then  remained  bright  enough  to  be  compared  with  Al- 
debaran.  From  other  sources  we  learn  that  the  diminu- 
tion of  light  went  on  for  5  years,  but  that  even  in  March, 
1843,  the  star's  lustre  continued  equal  to  that  of  an  ordi- 
nary 1st  magnitude  star.  At  about  that  time  a  new  outburst 
took  place,  and  according  to  the  observations  of  Mackey  at 
Calcutta,  and  Maclear  at  the  Cape,  rj  Argus  surpassed 
Canopus  and  scarcely  fell  short  of  Sirius  in  brilliancy. 
This  lasted  more  or  less  through  1844,  when  a  decline  in 
its  brilliancy  set  in.  This  proceeded,  however,  very  slow- 
ly, because  in  February,  1850,  Lieut.  Gilliss,  then  in  Chili, 
reported  rj  Argus  as  being  nearly  as  bright  as  Canopus 
but  of  a  reddish-yellow  colour,  somewhat  darker  than 
Mars.  In  1856  it  was  still  of  the  ist  mag.,  but  a  steady 
decline  was  evidently  in  progress.  Hence  we  find  that  in 
1858  it  was  rated  at  mag.  2|  by  Powell ;  in  i860  at  mag. 
3  by  Tebbutt:  in  1861  at  mag.  4J  by  Abbott;  in  1863  at 


90  THE  STORY  OF  THE  STARS. 

mag.  5  by  Ellery;  in  1867  at  mag.  6  by  Tebbutt.  Dur- 
ing the  next  10  years  it  fell  to  mag.  7,  and  in  March,  1886, 
was  rated  at  mag.  y^  by  Finlay  at  the  Cape  of  Good  Hope. 
This  appears  to  have  been  the  lowest  point,  for  by  May, 
1888,  the  light  had  increased  by  fully  half  a  magnitude, 
so  that  apparently  it  is  on  its  way  towards  another  maxi- 
mum, which  perhaps  may  be  expected  within  the  first  dec- 
ade of  the  20th  century.  From  the  foregoing  account  it 
is,  however,  clear  that  we  do  not  possess  sufficient  infor- 
mation to  assign  with  any  reasonable  degree  of  accuracy 
a  period  to  rj  Argus,  though  Wolf  has  suggested  46  years, 
and  Loomis  67  years.  Schonfeld,  however,  thinks  that 
the  star  has  no  regular  period  at  all.  At  any  rate  the 
maximum  stage  seems  very  complicated  and  to  consist  of 
3  maxima  which  jointly  occupy  25  years  of  the  period 
whatever  that  may  be.  During  this  sub-period,  the 
changes  may  perhaps  be  regarded  as  restricted  to  the  ist 
and  2nd  magnitudes,  and  this  sub-period  may  perhaps  be 
assumed  to  fall  something  like  in  the  mid-interval  between 
every  6th  or  7th  magnitude  minimum  of  the  star. 

T]  Argus  is  in  the  field  with  the  celebrated  "Great 
Nebula  in  Argo,"  and  some  remarkable  circumstances 
bearing  alike  on  the  star  and  on  the  nebula  will  come 
under  consideration  in  a  later  chapter  in  which  the  nebula 
will  be  described. 

The  reader  who  has  followed  me  thus  far  in  trying  to 
pick  up  some  ideas  about  the  peculiarities  of  the  stars 
called  "variable"  will  very  likely  wish  now  to  put  the 
question,  "  What  is  a  variable  star?  "  It  is  impossible  to 
answer  such  an  inquiry  with  any  confidence.  It  seems, 
however,  likely  that  the  variability  of  the  stars  which  are 
known  to  be  variable  may  be  due  to  one  of  two  causes, 
one  of  which  applies  to  one  class  of  star  and  the  other  to 
another  class.  It  is  generally  accepted  by  astronomers 
that  Algol  is  a  type  of  a  small  number  of  stars  which  owe 


VARIABLE  STARS.  9 1 

their  peculiarity  to  a  cause  quite  different  from  that  which 
applies  to  the  vast  majority  of  these  objects.  The  idea 
was  started  by  Pigott  in  1783,  and  has  met  with  much 
acceptance,  that  the  periodical  fluctuations  in  the  light  of 
Algol  are  due  to  the  revolution  round  it  of  an  opaque 
satellite  smaller  than  itself  yet  large  enough  to  eclipse 
partially  the  primary.  With  respect  to  the  general  run  of 
variables  it  is  thought  that  we  may  draw  some  inferences 
respecting  them  from  what  we  know  of  the  physical  con- 
stitution of  the  sun  and  of  what  happens  in  or  upon  that 
luminary.  Now  we  know  that  from  time  to  time,  and  ac- 
cording to  a  period  which  is  recognised  to  amount  to 
about  1 1  years,  dark  spots  of  various  sizes  and  shapes  and 
of  different  depths  of  shade  break  out  upon  the  sun.  The 
solar  spots  which  we  are  accustomed  to  see,  even  the  very 
largest  of  them,  are  too  small  relatively  to  the  size  and 
brilliancy  of  the  sun  to  cause  any  measurable  depreciation 
in  the  aggregate  of  the  sun's  light,  but  let  us  suppose  it 
were  otherwise,  and  that  every  1 1  years  masses  of  spots 
so  extensive  as  to  represent  one-half  or  even  one-fourth  of 
the  apparent  surface  of  the  sun,  burst  forth,  we  should 
then  have  the  great  centre  of  our  system  converted  from 
a  permanently  bright  star  into  a  variable  star.  I  speak  of 
our  sun  as  a  bright  star  because  probably  it  represents  for 
us  on  the  earth  neither  less  nor  more  than  what  Sirius  or 
other  bright  stars  *  represent  to  the  inhabitants  of  other 
worlds  in  far-off  regions  of  space.  If  we  could  travel  from 
the  earth  a  long  way  towards  Sirius  we  should  probably 
find  Sirius  to  grow  into  what  we  should  without  reserva- 
tion call  a  sun,  whilst  our  sun  would  deteriorate  into  what 
we  now  call  a  star. 

So  much  for  the  possible  circumstances  of  those  stars 
which  undergo  periodic  changes  of  light.     But  this  expla- 

*  See  p.  58  {ante). 


92         THE  STORY  OF  THE  STARS. 

nation,  even  if  accepted  so  far,  does  not  meet  the  case  of 
those  temporary  outbursts  of  stellar  light  which  we  con- 
sidered in  Chapter  XI.  {a?tte).  Here  again,  however,  solar 
history  may  be  brought  in.  It  is  now  quite  recognised  as 
a  fact  that  the  red  flames  seen  during  total  eclipses  of  the 
sun  are  outbursts  of  glowing  hydrogen  gas  emanating 
from  the  interior  of  the  sun  ;  nay,  more,  that  such  emana- 
tions of  burning  hydrogen  are  constantly  occurring  on  the 
sun.  Now  in  the  case  of  the  temporary  star  in  Corcna 
Borealis  which  became  visible  in  1866,  Huggins's  observa- 
tions tended  to  show  that  there  happened  in  that  star  a 
sudden  and  extraordinary  outburst  of  glowing  hydrogen, 
which  by  its  own  light,  as  well  perhaps  as  by  heating  up 
the  whole  surface  of  the  star,  caused  the  unwonted  in- 
crease in  its  brilliancy  which  then  took  place.  These 
ideas  find  confirmation  in  other  directions,  but  it  seems 
hardly  within  the  design  of  this  work  to  go  further  into 
details  of  this  character. 

There  are,  however,  some  miscellaneous  facts  con- 
nected with  variable  stars  which  are  too  interesting  to  be 
passed  over.  For  instance,  it  is  an  undoubted  fact  that 
the  vast  majority  of  the  variable  stars  are  red  or  reddish 
in  colour  ;  and  so  general  is  this  rule  that  whenever  a  new 
star  is  found  it  is  a  safe  presumption  to  start  with  that  if 
its  colour  is  red  it  has  hitherto  escaped  observation  be- 
cause of  its  being  variable.  Hind  has  noticed  that  vari- 
able stars  when  at  minimum  often  appear  hazy  or  foggy,  on 
which  Arago  suggested  the  idea  that  the  diminution  of 
brilliancy  might  be  due  to  the  interference  of  clouds.  It 
is  an  undoubted  fact  that  in  the  case  of  red  variable  stars 
as  they  diminish  in  brilliancy  they  deepen  in  colour,  whilst 
as  their  light  increases  their  hue  becomes  paler. 

An  experienced  American  observer.  Chandler,  has 
evolved  a  connection  between  the  colours  and  periods  of 
variable  stars.     He  not  only  subscribes   to  the  opinion 


VARIABLE  STARS.  93 

that  variable  stars  are  generally  red,  but  he  finds  that  the 
more  red  they  are  the  longer  their  periods.  Of  112  vari- 
ables whose  colours  and  periods  are  fairly  well  estab- 
lished, classifying  them  in  groups  having  periods  of  under 
100  days,  of  100  days  but  under  200,  and  so  on  up  to 
over  400,  he  finds  that  whilst  of  those  under  100  days 
barely  one-half  are  red,  of  those  over  100  days  three- 
fourths  are  red  ;  whilst  those  over  400  days  are  all  red. 
His  statistics  arranged  in  another  form  show  that  whilst 
the  periods  of  the  white  and  yellow  stars  average  125 
days,  the  periods  of  the  red  stars  average  288  days,  and  of 
the  intense  red  477  days. 

Espin  has  arrived  at  some  curious  statistics  concern- 
ing the  distribution  of  variable  stars  in  the  heavens,  and 
also  concerning  their  periods.  He  finds  that  they  are 
especially  numerous  in  a  zone  of  the  heavens  inclined  15° 
or  20°  to  the  equator ;  that  this  zone  crosses  the  preced- 
ing side  of  the  Milky  Way  on  the  N.  side  of  the  equator, 
and  the  following  side  of  the  Milky  Way  on  the  S.  side  of 
the  equator  ;  that  the  northern  portion  of  the  zone  is  not 
many  degrees  broad  and  is  clearly  marked,  but  that  the 
southern  portion  is  split  into  2  streams  of  stars  and  that 
the  place  where  this  occurs  is  near  the  place  where  the 
Milky  Way  is  also  divided  ;  that  hereabouts  the  variables 
seem  connected  with  the  Milky  Way,  often  occurring  in 
the  gaps  and  constantly  on  the  edges  of  the  gaps,  but 
rarely  in  the  centre  of  the  star  sprays  from  the  Milky 
Way ;  whilst  the  northern  stream  of  variable  stars  is 
sharply  defined  by  itself  and  seems  unconnected  with  the 
Milky  Way.  Espin  adds  that  with  one  or  two  exceptions 
all  the  temporary  stars  have  appeared  in  the  region  where 
the  Milky  Way  and  the  variable  star  zone  are  both 
broken  into  two  streams  ;  and  that  stars  which  do  not 
belong  to  the  above-named  zone  are  chiefly  the  bright 
and    short-period    variables.     Espin's   statistics   in   detail 


94  THE  STORY  OF  THE  STARS. 

are  too  elaborate  for  embodiment  in  these  pages  in  their 
entirety,  but  some  further  general  conclusions  are  of 
sufficient  interest  and  importance  to  be  reproduced. 
Writing  in  1882  he  found  that  the  variables  then  known 
readily  fell  into  two  classes  :  (i)  those  with  periods  of 
less  than  70  days  ;  and  (2)  those  with  periods  of  more 
than  135  days  ;  there  being  none  with  periods  between  71 
and  135  days.  Of  the  former  group  it  might  be  said 
that  they  were  in  colour  white  or  red  in  tolerably  even 
numbers,  and  large  in  magnitude  ;  whilst  the  latter  group 
were  mainly  red  and  small  in  magnitude. 

Some  other  conclusions  which  he  arrived  at  were  that 
if  the  variation  of  light  be  small  in  extent,  or  if  the  star  be 
bright,  the  period  will  probably  be  short ;  on  the  other 
hand,  where  the  period  ranges  from  135  days  up  to  420 
days  the  number  of  stars  increases  with  the  length  of  the 
period  ;  also,  that  between  a  range  of  i  magnitude  up  to 
6  magnitudes  the  number  of  stars  increases  with  the  vari- 
ation in  magnitude.  These  rules  seem,  however,  to  fail 
where  the  stars  have  periods  of  more  than  420  days,  or 
where  the  range  extends  beyond  6  magnitudes. 

The  foregoing  statistics  are  based  upon  only  a  minority 
of  the  known  variables,  and  therefore  cannot  yet  be  put 
forward  as  disclosing  a  series  of  general  laws.  Neverthe- 
less, they  are  sufficiently  interesting  and  pronounced  to  de- 
serve attention  now,  as  well  as  to  encourage  further  in- 
quiry in  the  future. 

The  following  classification  of  variable  stars  has  met 
with  some  acceptance  in  America,  and  therefore  it  may  be 
given  here,  but  it  is  open  to  the  objection  that  it  assumes 
that  temporary  stars  are  merely  long-period  variables, 
which  at  present  is,  at  the  best,  an  assumption  : — 

(i)  Stars  showing  slow  continuous  change. 

(2)  Stars  exhibiting  irregular  fluctuations  of  light :  al- 


THE  STARS  IN  POETRY.  95 

ternately  brightening  up  and  becoming  dim  with- 
out any  apparent  law. 

(3)  Temporary  stars,  which  blaze  out  suddenly  and 

then  disappear. 

(4)  Periodic  stars  of  the  type  of  0  Ceti,  usually  of  long 

period. 

(5)  Periodic   stars   of  the   type   of  /3  Lyrse,  of  short 

period. 

(6)  Periodic  stars  of  the  type  of  Algol,  in  which  the 

variation  of  light  is  such  as  would  result  from 
some   intervening    body   eclipsing    the   primary 
star. 
It  is  evident  from  all  that  has  gone  before  that  variable 
stars  form  a  very  interesting  branch  of  observational  as- 
tronomy. 


CHAPTER  XIII. 

THE   STARS   IN   POETRY. 

As  the  previous  chapter  concludes  what  I  have  to  say 
respecting  the  stars  taken  individually,  and  the  remainder 
;of  this  volume  will  be  occupied  with  the  stars  in  masses 
under  the  designations  Clusters  and  Nebulae,  the  present 
seems  a  convenient  point  at  which  to  withdraw  the  reader's 
thoughts  for  a  while  from  the  technicalities  of  science  to 
things  more  light  and  sentimental.  Hence  it  has  occurred 
to  me  to  try  and  enliven  my  pages  by  a  few  citations  from 
English  classical  poetry — a  field  which  has  been  worked 
with  great  assiduity,  from  an  astronomer's  standpoint,  by 
Mr.  J.  E.  Gore.* 

Shakespeare  of  course  occupies  the  front  rank  amongst 
the  great  English  writers  who  have  brought  the  facts  of 

*  In  his  Scenery  o/the  Heavens. 


96         THE  STORY  OF  THE  STARS. 

science,  astronomical  and  general,  into  line  with  their  or- 
dinary musings.  Unfortunately  he  lived  at  a  period  when 
the  so-called  science  of  astrology  flourished  side  by  side 
with  astronomy,  and  trading  as  it  did  on  the  credulity  of 
man  it  overshadowed  but  too  successfully  the  sister  science 
of  astronomy,  if  such  a  bracketing  together  of  fraud  and 
humbug  with  true  learning  can  be  tolerated.  Perhaps, 
after  all,  we  of  the  19th  century  must  not  be  too  hard  on 
our  forefathers  of  the  Elizabethan  epoch,  for  figures  of 
speech  implying  a  belief  in  the  tenets  of  astrology  and  in 
many  other  ridiculous  beliefs  and  practices  hold  sway  in 
these  closing  years  of  the  century,  and  they  are  not  re- 
stricted to  ignorant  and  unlettered  dwellers  in  remote 
agricultural  villages. 

And  now  to  Shakespeare.     In  Julius  Ccesar  (Act  i., 
scene  2)  Cassius  says — 

•*  Men  at  some  times  are  masters  of  their  fates  ; 
The  fault,  dear  Brutus,  is  not  in  our  stars 
But  in  ourselves,  that  we  are  underlings." 

The  idea  that  the  stars  exercise  some  influence,  for  weal 
or  woe,  over  the  birth  of  individuals  was  widely  prevalent 
300  years  ago,  and  Shakespeare  does  no  more  than  con- 
form to  the  ideas  of  the  times  when  he  makes  Richard  III. 
say  (Act  iv.,  scene  4) — 

'  *  Lo,  at  their  births  good  stars  were  opposite  ; " 

or  Jupiter,  in  Cymbeline,  say  (Act  v.,  scene  4) — 

"  Our  Jovial  star  reign'd  at  his  birth  ; " 

whilst  Romeo  (Act  v.,  scene  3)  speaks  in  the  Churchyard 
scene  of  shaking — 

*•  The  yoke  of  inauspicious  stars." 


THE  STARS  IN  POETRY.  97 

Malvolio,  in  Twelfth  Night  (Act  ii.,  scene  5),  expresses 
the  popular  sentiment  in  words  most  clear — 

"  In  my  stars  I  am  above  thee  ;  but  be  not  afraid  o*"  greats 
ness  ;  " 

and  then  follow  immediately  the  familiar  sentiments — 

"  Some  are  born  great,  some  achieve  greatness,  and  some  have 
greatness  thrust  upon  them." 

Particular  constellations  or  groups  of  stars  are  occa- 
sionally referred  to  by  Shakespeare.  Thus  in  Othello 
(Act  ii.,  scene  i)  the  sea,  stirred  by  the  wind,  is  said  to — 

*'  Seem  to  cast  water  on  the  burning  Bear, 
And  quench  the  Guards  of  the  ever-fixed  Pole." 

What  idea  underlies  the  apphcation  of  the  term  "  burning  " 
to  Ursa  Major  does  not  appear. 

The  Pole  Star  receives  elaborate  treatment  in  Julius 
Ccssar  (Act  lii.,  scene  i).     Caesar  himself  thus  speaks — 

**  But  I  am  constant  as  the  northern  star, 
Of  whose  true-fix'd  and  resting  quality 
There  is  no  fellow  in  the  firmament. 
The  skies  are  painted  with  unnumber'd  sparks, 
They  are  all  fire,  and  every  one  doth  shine  ; 
But  there's  but  one  in  all  doth  hold  his  place." 

In  the  letter  read  by  Polonius  {Hamlet,  Act  ii.,  scene  2) 
we  come  upon  an  idea  which  is  alike  ancient  (for  Stoics 
and  Epicureans  held  it)  and  modern — 

"  Doubt  thou  the  stars  are  fire  : 
Doubt  that  the  sun  doth  move." 

Milton  is  another  of  our  great  national  writers  who 
makes  various  allusions  to  celestial  objects.  In  the  Para-, 
dise  Lost  (Book  vii.)  he  refers  to  the  moon  and  stars — 

7 


98  THE  STORY  OF  THE  STARS. 

"...  then  formed  the  moon 
Globose,  and  every  magnitude  of  stars, 
And  sowed  with  stars  the  heavens,  thick  as  a  field  ;  " 

and  to  the  Pleiades  (in  the  same  book) — 

"...  the  gray 
Dawn,  and  the  Pleiades,  before  him  danced, 
Shedding  sweet  influence." 

Young's  Night  Thoughts  is  peculiarly  rich  in  its  ref- 
erences to  astronomy.  Perhaps  the  best-known  passage 
of  all  is  that  in  the  "  9th  Night,"  which  runs  as  follows : — 

'*  Devotion  !     Daughter  of  Astronomy, 
An  undevout  Astronomer  is  mad. 
True  ;  All  Things  speak  a  God  ;  but  in  the  Small 
Men  trace  out  Him  ;  in  Great  He  seizes  Man." 

In  the  following  passage  ("  8th  Night  ")  we  come  upon 
the  idea  already  mentioned  in  these  pages  as  being  a  sober 
astronomical  probability — 

"  These  sparks  of  night,  these  stars  shall  shine, 
Unnumber'd  Suns." 

Again,  the  following  passage  referring  to  the  distances  of 
the  stars  contains,  as  we  have  seen,  true  astronomical 
teaching — 

"  How  distant  some  of  these  nocturnal  Suns  ! 
So  distant  (says  the  Sage)  'twere  not  absurd 
To  doubt,  if  Beams  set  out  at  Nature's  Birth, 
Are  yet  arrived  at  this  so  foreign  World 
Tho'  nothing  half  so  rapid  as  their  Flight." 

Truly  indeed  may  it  be  said  that  the  stars  serve  the  pur- 
pose thus  suggested  by  Young — 


THE  STARS  IN  POETRY.  99 

"  One  Sun  by  Day,  by  Night  ten  thousand  shine 
And  light  us  deep  into  the  Deity." 

In  Byron's  Childe  Harold's  Pilgrimage  (Canto  III., 
V.  Ixxxviii.)  we  find  the  following  striking  passage  : — 

"  Ye  stars  !  which  are  the  poetry  of  heaven  ! 
If  in  your  bright  leaves  we  would  read  the  fate 
Of  men  and  empires — 'tis  to  be  forgiven 
That  in  our  aspirations  to  be  great, 
Our  destinies  o'erleap  their  mortal  state 
And  claim  a  kindred  with  you  ;  for  ye  are 
A  beauty  and  a  mystery,  and  create 
In  us  such  love  and  reverence  from  afar, 
That  fortune,  fame,  power,  life,  have   named  themselves  a 
star." 

Shelley  in  his  Prometheus   Unbound  (Act  iv.),  speak- 
ing of  an  astronomer  in  his  observatory,  says — 

"  Heaven's  utmost  deep 
Gives  up  her  stars,  and  like  a  flock  of  sheep 
They  pass  before  his  eye,  are  number'd,  and  roll  on." 

Moore  in  his  Light  of  the  Harain  thus  brings  in  the 
Pole  Star— 

"  Whose  light,  among  so  many  lights, 
Was  like  that  star,  on  starry  nights 
The  seaman  singles  from  the  sky, 
To  steer  his  bark  for  ever  by  !  " 

Elsewhere  {^Sacred  Songs)  he  makes  a  further  allusion  to 
the  Pole  Star— 

"As  still  to  the  star  of  its  worship,  though  clouded, 
The  needle  points  faithfully  o'er  the  dim  sea." 


lOO  THE   STORY  OF   THE  STARS. 

By  the  way,  this  allusion  is  not  scientifically  accurate, 
for  the  compass-needle  does  not  point  to  the  Pole  Star, 
but  to  the  earth's  magnetic  pole. 

The  stars  naturally  find  a  place  in  Thomson's  Seasons. 
He  says — 

"  Snatch  me  to  heaven  ;  thy  rolling  wonders  there, 
World  beyond  world,  in  infinite  extent, 
Profusely  scatter'd  o'er  the  blue  immense, 
Show  me  :  their  motions,  periods,  and  their  laws, 
Give  me  to  scan." 

Longfellow  remarks — 

"  Wondrous  truths,  and  manifold  as  wondrous, 
God  hath  written  in  those  stars  above." 

Wordsworth,  in  The  Excursion  (Book  IV.)  thus 
*Drings  in  the  uses  of  the  Pole  Star — 

"  Chaldean  shepherds,  ranging  trackless  fields, 
Beneath  the  concave  of  unclouded  skies 
Spread  like  a  sea,  in  boundless  solitude 
Looked  on  the  polar  star,  as  on  a  guide 
And  guardian  of  their  course,  that  never  closed 
His  steadfast  eye." 

And  in  Poems  of  the  Imagination  (Part  II.,  xxv.) — 

"  The  stars  are  mansions  built  by  Nature's  hand 
And,  haply,  there  the  spirits  of  the  blest 
Dwell  clothed  in  radiance,  their  immortal  vest." 

Tennyson  is  very  astronomical.  In  The  Princess  we 
€nd — 

"  And  the  shining  daffodil  dies,  and  the  Charioteer 
And  starry  Gemini  hang  like  glorious  crowns 
Over  Orion's  grave  low  down  in  the  west." 


GROUPS  OF  STARS.  lOI 

Tennyson  has  a  very  good  conception  of  a  binary  star 
when  he  speaks  of — 

"  those  double  stars 
Whereof  the  one  more  bright 
Is  circled  by  the  other." 


CHAPTER    XIV. 
GROUPS   OF   STARS. 

The  thing  to  do  in  order  to  be  able  to  reahse  to  the 
utmost  the  marvellous  beauty  of  the  starry  heavens,  is  to 
obtain  an  opportunity  of  gazing  at  some  of  those  crow^ded 
fields  of  stars  bordering  on  the  Milky  Way,  in  which  the 
stars  are  so  close  together  that  though  they  hardly  consti- 
tute a  "  cluster  "  technically  so-called,  are  yet  so  numer- 
ous that  the  whole  circular  field  of  the  telescope  is  one 
shining  mass  of  bright  points.  There  is  such  a  field, 
favourably  circumstanced  for  observers  in  England  in  the 
constellation  Perseus  (R.  A.  2h.  iim.  20s.  Decl.  +  56°  38'), 
and  I  would  urge  every  reader  of  this  book  to  take  the 
first  opportunity  open  to  him  of  viewing  this  in  a  telescope 
of,  if  possible,  not  less  than  3  inches  aperture.  Doing 
this  he  will,  I  am  confident,  be  more  inspired  to  dedicate 
to  astronomy  some  of  his  time,  thoughts,  and  money,  than 
by  doing  anything  else  which  I  could  suggest.  This  par- 
ticular object  is  sometimes  called  "  The  Cluster  in  the 
Sword  Handle  of  Perseus." 

Starting  with  the  stars  as  single  stars  we  have  seen 
that  a  considerable  number  go  together  in  pairs ;  that  a 
smaller  number  are  associated  in  triplets ;  and  so  on,  till 
we  come  to  a  principal  star  having,  it  may  be,  half  a  dozen 
companions  gathered  round  it.     The  transition  from  such 


102  THE  STORY  OF  THE   STARS. 

a  group  to  what  is  called  a  "  cluster,"  and  so  on  to  a  "  re- 
solvable nebula,"  is  a  gradual  one  which,  however,  may 
be  said  to  come  about  in  the  nature  of  things  almost  as  a 
matter  of  course.  The  lines  of  demarcation  between 
these  different  classes  of  objects  are  naturally  not  very 
pronounced,  and  must  be  laid  down  in  a  rather  arbitrary 
manner.  However,  I  think  that  for  our  present  purpose 
we  may  conveniently  range  the  celestial  objects  now 
about  to  be  described  under  the  three  following  heads  : — 
(i)  Irregular  groups  more  or  less  visible  to  the  naked  eye ; 
(2)  Clusters  of  stars  resolvable  into  their  constituent  stars, 
with  the  aid  of  a  telescope  ;  (3)  Nebulas  for  the  most  part 
irresolvable  with  the  telescopes  we  at  present  possess; 
■either  because  the  telescopes  are  deficient  in  the  neces- 
sary optical  power,  or  because  the  objects  themselves  are 
not  stellar  at  all,  but  are  something  else — gaseous  or  what 
not. 

Of  the  groups  of  stars  which  may  be  considered  to  be 
incipient  clusters  there  are  several  visible  to  the  naked 
eye,  not  counting  certain  true  nebulae  which  can  be  de- 
tected by  the  naked  eye  by  reason  of  their  great  size. 
Three  of  these  clusters  were  noticed  and  recorded  by  the 
ancients,  namely,  the  "  Pleiades  "  and  "  Hyades  "  in  Tau- 
rus, and  '•  Praesepe  "  in  Cancer.  The  Pleiades  are  men- 
tioned twice  in  the  Book  of  Job,  and  once  in  the  prophecy 
of  Amos,  and  also  in  Homer,  who  likewise  names  the 
Hyades.  The  passages  in  Job  and  Amos  have  already 
been  quoted.*  The  passage  in  Homer  (Odyssey  Lib.  v. 
ver.  270)  runs  thus  in  Pope's  version  : — 

"  With  beating  heart  Ulysses  spreads  his  sails  ; 
Plac'd  at  the  helm  he  sat,  and  mark'd  the  skies. 
Nor  clos'd  in  sleep  his  ever-watchful  eyes. 

*  Ante,  p.  40. 


GROUPS  OF  STARS.  103 

There  vievv'd  the  Pleiads,  and  the  northern  team, 
And  great  Orion's  more  refulgent  beam, 
To  which,  around  the  axle  of  the  sky 
The  bear  revolving,  points  his  golden  eye." 

The  Pleiades  were  always  supposed  to  be  7  in  num- 
ber; then  one  was  said  to  have  disappeared,  so  that  6 
only  remained.  This  transaction  appears  to  be  lost  in 
obscurity ;  I  had  even  said  is  unhistoric.  Yet  Ovid  has 
recorded  it  in  the  famous  line  : — 

"  Quae  Septem  dici,  sex  tamen  esse  solent." 

However,  whilst  ordinary  eyes  can,  as  a  rule,  only  grasp 
6  stars,  the  7th  is  still  there,  and  can  be  seen  with  the 
slightest  optical  help  ;  whilst  very  good  eyes  can  make  out 
several  more.  Miss  Airy,  indeed,  has  noted  12.  With  a 
small  telescope  any  number  (say  at  least  50)  may  be  seen, 
and  photography  has  recorded  over  2000  stars.  The 
brightest  in  the  group  is  Alcyone,  otherwise  r]  Tauri,  of 
the  3rd  magnitude  ;  next  in  order  come  Electra  and  Atlas, 
both  3|>  Maia  4,  Merope  \\,  Taygeta  \\ ;  whilst  Celeno, 
Asterope,  and  Pleione  are  all  smaller  and  of  much  the 
same  brightness,  say  mag.  6.  Then  follows  a  miscellane- 
ous crowd  of  smaller  stars. 

A  passing  allusion  must  be  made  to  certain  modern 
discoveries  connected  with  the  Pleiades,  the  exact  import 
of  which  is  at  present  very  imperfectly  understood.  On 
October  19,  1859,  Tempel,  a  German  observer  resident  in 
Italy,  observed  an  object  which  he  took  to  be  a  telescopic 
comet.  On  the  following  evening  he  found  it  in  the  same 
position,  and  therefore  not  a  moving  comet,  but  a  station- 
ary nebula.  It  was  seen  subsequently  by  other  observers. 
Auwers  noted  it  to  be  about  J"  in  extent,  but  thought 
that  it  might  have  escaped  notice  owing  to  its  proximity  to 
Merope,  one  of  the  Pleiades,  the  bright  light  of  which 


X04  THE  STORY  OF  THE  STARS. 

would  overshadow  the  nebula.     Schiaparelli  in  1875  saw 
the  nebula  very  clearly,  and  was  much  surprised  at  its 


Fig.  12.— The  Pleiades. 

size  and  apparent  ramifications  in  different  directions, 
Hind  had  stated  that  he  had  often  suspected  nebulosity 
around  some  of  the  smaller  outlying  stars  of  the  Pleiades. 
The  earlier  observations  of  this  nebula  (or  these  nebulae) 


GROUPS  OF  STARS.  1 05 

in  the  Pleiades  were  by  no  means  very  consistent,  and  the 
idea  of  variability  suggested  itself ;  some  even  regarded 
the  whole  thing  as  a  myth.  But  later  researches  by  the 
aid  of  photography  have  not  only  established  the  reality 
of  Tempel's  discovery,  but  have  done  a  good  deal  more  ; 
for  it  is  now  certain  that  no  fewer  than  five  of  the  chief 
stars  in  the  Pleiades  (Pleione,  Atlas,  Asterope,  and  Tay- 
geta  being  the  exceptions)  are  involved  in  a  mass  of  nebu- 
lous matter,  the  extent  of  which  was  never  suspected 
until  the  photographic  proof  was  obtained  at  Paris  in 
1885.  It  is  satisfactory,  under  the  circfumstances,  to  know 
that  a  general  confirmation  of  the  photograph  has  been 
obtained  by  the  direct  testimony  of  the  telescope  in  the 
shape  of  eye-views  at  the  Russian  observatory  at  Pul- 
kowa,  with  the  gigantic  refractor  of  .30  inches  aperture 
there  in  use. 

The  Hyades  form  a  more  open  and  less  interesting 
group,  also  in  the  constellation  Taurus,  and  near  Alde- 
bar^n ;  but  the  stars  are  too  scattered  to  make  a  very 
striking  field. 

Praesepe  in  Cancer  is  altogether  a  more  effective  group ; 
one,  however,  which  should  be  looked  at  through  a  tele- 
scope with  a  low  power  and  large  field.  This  object,  long 
called  the  "  Bee-hive,"  appears  to  have  been  the  first  ob- 
ject to  which  the  term  "  nebula "  was  applied  in  bygone 
days,  its  component  stars  not  being  separately  distinguish- 
able. We  have  it  on  record  that  Prassepe  was  taken 
account  of  by  the  ancients  2000  years  ago ;  for  both 
Aratus  and  Theophrastus  tell  us  that  its  dimness  and  dis- 
appearance during  the  progressive  condensation  of  the 
atmosphere  were  regarded  as  the  first  sign  of  approaching 
rain.  Galileo  with  his  baby  telescope  counted  36  stars. 
To  find  Prassepe,  carry  an  imaginary  line  from  Spica 
Virginis  under  Regulus  in  Leo,  and  about  22°  beyond  it 
will  strike  Praesepe. 


Io6  THE  STORY  OF  THE  STARS. 

The  group  of  stars  forming  the  constellation  Coma 
Berenices  is  cited  by  Webb  as  "  a  gathering  of  small  stars 
which  obviously  at  a  sufficient  distance  would  become  a 
nebula  to  the  naked  eye."  By  the  way,  this  constellation 
is  said  to  have  been  instituted  by  the  astronomer  Conon 
in  honour  of  the  Queen  of  Ptolemy  Soter,  who  dedicated 
her  splendid  tresses  to  the  gods  to  secure  her  husband's 
safety  in  war! 


CHAPTER   XV. 

CLUSTERS   OF   STARS. 

We  have  now  to  consider  the  clusters  of  stars  which, 
though  seemingly  nebulous  in  very  small  telescopes,  be- 
come immediately  resolved  into  individual  stars  on  the 
application  of  a  very  slight  additional  amount  of  optic*^ 
power.  A  select  number  of  these  are  put  together  in  tht 
Appendix  for  the  use  of  those  readers  of  this  book  who, 
possessing  telescopes,  would  wish  to  know  whither  to 
direct  them  profitably.  It  will  suffice,  therefore,  to  allude 
here  to  only  a  few  of  these  clusters.  31  ip  VI.  Cassiopeias 
is  a  somewhat  conspicuous  object  and  readily  seen  with  a 
telescope  of  2  inches  aperture.  Perhaps  the  best  known 
of  all  the  so-called  globular  clusters  is  13  M.  Herculis,  that 
is  to  say,  the  13th  in  Messier 's  Catalogue  and  in  the  con- 
stellation Hercules.  This  is  commonly  regarded  as  the 
finest  of  the  globular  clusters.  Smyth  called  it  "  an  ex- 
tensive and  magnificent  mass  of  stars  with  the  most  com- 
pressed part  densely  compacted  and  wedged  together 
under  unknown  laws  of  aggregation."  Sir  J,  Herschel 
spoke  of  its  thousands  of  stars  and  "  hairy-looking  curvi- 
linear branches,"  which  features  the  Earl  of  Rosse  inter- 
preted as  indicative  of  a  spiral  tendency  ;  he  also  perceived 


CLUSTERS  OF  STARS.  107 

several  dark  rifts  in  the  cluster.  Beautiful  as  it  is — one 
might  even  say  magnificent — yet  J.  P.  Nichol  goes  a  little 
too  far  in  asserting  that  "  perhaps  no  one  ever  sav^  it  for 
the  first  time  through  a  telescope  without  uttering  a  shout 
of  wonder." 

Before  offering  any  further  remarks  on  the  larger  clus- 
ters it  will  be  convenient  to  explain  the  word  "globular," 


Fig.  13.— 13  M.  HercuHs. 

and  seemly  to  say  something  about  the  French  astrono- 
mer Messier,  whose  name  is  so  closely  associated  with 
these  objects.  "  Globular,"  as  a  word,  of  course  needs 
no  explanation,  but  it  was  first  applied  to  star  clusters,  I 
believe,  by  Sir  W.  Herschel,  in  order  to  convey  to  the 
mind  the  idea  that,  when  looking  at  them,  the  eye  is  gaz- 
ing not  on  a  flat  background  sprinkled  with  stars,  but  on 
a  veritable  ball  of  stars.  Without  saying  that  all  or  even 
any  of  the  clusters  so  called  are  truly  such,  yet  undoubt- 
edly an  ordinary  eye  will  readily  appreciate  them  as  balls 
of  stars. 


Io8  THE  STORY  OF  THE  STARS. 

Messier  was  a  Frenchman  who  dedicated  himself  about 
a  century  ago  to  the  task  of  hunting  for  comets.  In  car- 
rying out  this  work  he  was  so  far  very  successful  that  be- 
tween 1760  and  1798  he  found  no  fewer  than  13.  He 
was,  however,  much  bothered  by  constantly  coming  upon 
objects  in  his  small  telescope  which,  whilst  they  looked  at 
first  Uke  comets,  were  only  clusters  and  nebulse ;  so  in 
1758  he  thought  to  guard  against  being  taken  in  any  more 
by  forming  a  permanent  catalogue  of  nebulse,  including 
clusters,  by  collecting  together  all  that  had  been  found  by 
himself,  La  Caille,  and  Mechain.  This  catalogue  was 
published  (but  whether  for  the  first  time  or  not  I  am  not 
sure)  in  1784,  and  is  alike  a  monument  of  its  author's 
shrewdness  and  of  his  industry,  for  it  embraces,  with 
scarcely  an  exception,  the  whole  of  the  conspicuous  clus- 
ters and  nebulas  visible  in  the  latitude  of  Paris. 

We  will  now  resume  our  consideration  of  the  clusters 
by  mentioning  a  few  more  of  them.  Next  after  the  clus- 
ter in  Hercules  comes  perhaps  5  M.  Libras,  which,  in  the 
words  of  Webb,  is  a  "  beautiful  assemblage  of  minute 
stars  greatly  compressed  in  the  centre."  Sir  W.  Herschel 
with  his  40-ft.  reflector  made  out  about  200  stars,  though 
^.he  middle  of  it  was  so  compressed  that  it  was  impossible 
to  individualise  the  components.  Smyth  says  that : — 
"This  superb  object  is  a  noble  mass,  refreshing  to  the 
senses  after  searching  for  faint  objects,  with  outliers  in  all 
directions  and  a  bright  central  blaze."  Messier,  however, 
"assured  himself  that  it  did  not  contain  a  single  star," 
but  this  unsound  statement  was  the  unwise  result  of  dog- 
matising, on  the  strength  of  a  telescope  2  feet  long. 

80  M.  Scorpii  is  a  compressed  globular  cluster  which 
Messier,  who  found  it  in  1780,  described  as  resembling 
the  nucleus  of  a  comet ;  and  indeed  its  blazing  centre  and 
attenuated  disc  give  it  a  very  cometary  aspect.  Sir  W. 
Herschel  pronounced  it  to  be  the  richest  and  most  con- 


CLUSTERS  OF  STARS.  1 09 

densed  mass  of  stars  which  the  firmament  can  offer  to 
the  contemplation  of  astronomers,  albeit  that  Messier  had 


Fig.  14. — 5  M.  Librae. 

registered  it  as  Nebuleuse  sans  dtoiles.  Near  the  centre  of 
this  object,  or,  as  Webb  suggested,  "  between  it  and  us," 
there  burst  forth  in  i860  a  remarkable  temporary  star. 
Pogson  had  been  familiar  with  the  cluster  because  two 
variable  stars,  R  and  S  Scorpii,  were  in  the  field  with  it, 
and  he  had  frequently  been  in  the  habit  of  viewing  them. 
On  May  28,  1 860,  while  seeking  for  these  variables,  his  at- 
tention was  arrested  by  the  fact  that  a  star  of  about  the 
7th  magnitude  had  appeared  in  the  place  previously  occu- 
pied by  the  cluster.  He  had  seen  the  cluster  as  recently 
as  May  9,  and  was  positive  that  it  had  appeared  exactly  the 
same  as  usual  without  anything  stellar  about  it.  The 
same  instrument  and  power  had  been  employed  on  both 
occasions.  A  fortnight  later,  that  is,  on  June  10,  using  a 
.lower  power,  the  stellar  appearance  had  nearly  vanished, 
but  the  cluster  still  shone  with  unusual  brilliancy  and  a 


no  THE  STORY  OF  THE  STARS. 

marked  central  condensation.  Pogson's  observations  were 
fully  confirmed  by  two  German  observers.  £.  Luther  and 
Auwers.  Pogson  thus  summed  up  the  circumstances  of 
this  curious  case  : — "  It  is  therefore  incontestably  proved 
upon  the  evidence  of  3  witnesses  that  between  May  9  and 
June  10  [i860]  the  cluster  known  as  80  Messier  changed 
apparently  from  a  pale  cometary-looking  object  to  a  well- 
defined  star  fully  of  the  7th  magnitude,  and  then  returned 
to  its  usual  and  original  appearance.  It  seems  to  me  ab- 
surd to  attribute  this  phenomena  to  actual  change  in  the 


Fig.  15. — 80  M.  Scorpii. 

cluster  itself,  but  it  is  very  strange  if  a  new  variable  star, 
the  3rd  in  the  same  field  of  view,  should  be  situated  be- 
tween us  and  the  centre  of  the  cluster."  At  the  time 
when  this  was  written  the  incident  thus  narrated  was 
unique,  but  the  more  recent  case  of  Nova  Andromedas  ap- 
pears to  present  various  analogies  to  the  case  of  80  M. 
Scorpii  in  i860.  Schonfeld  thought  he  saw  some  trace  of 
the  star  in  June,  1869,  but,  barring  this,  I  am  not  aware  of 
any  further  information  being  on  record.     There  are  many 


CLUSTERS  OF  STARS.  1 1 1 

Other  globular  clusters  to  be  met  with  in  the  heavens, 
some  which  will  be  found  referred  to  in  the  List  in  the 
Appendix,  but  2  more  only  need  be  mentioned  here. 
These  are  both  in  the  southern  hemisphere,  and  surpass, 
it  would  seem  in  the  matter  of  size  and  brilliancy,  anything 
visible  in  England. 

47  Toucani  was  described  by  Sir  J.  Herschel  as  a  su- 
perb globular  cluster  "  very  visible  to  the  naked  eye  and 
one  of  the  finest  objects  in  the  heavens.  It  consists  of  a 
very  condensed  spherical  mass  of  stars  of  a  pale  rose- 
colour  concentrically  enclosed  in  a  much  less  condensed 
globe  of  white  ones  15'  or  20'  in  diameter."  Herschel,  in 
speaking  of  this  cluster,  made  the  very  curious  and  sig- 
nificant remark  that  he  could  not  remember  a  single  ellip- 
tical nebula  which  is  resolvable,  all  the  resolvable  clusters 
being  more  or  less  circular  in  form.  He  then  goes  on  to 
add  : — "  Between  these  two  characters  then  (ellipticity  of 
form  and  difficulty  of  resolution)  there  undoubtedly  exists 
some  physical  connection  ...  it  deserves  also  to  be  no- 
ticed that  in  very  elliptic  nebulas  which  have  a  spherical 
centre  (as  in  65  M.)  a  resolvable  or  mottled  character  of- 
ten distinguishes  the  central  portion,  while  the  branches 
exhibit  nothing  of  the  kind."  This  was  written  prior  to 
the  construction  of  Lord  Rosse's  great  telescope,  and 
therefore  it  is  no  reflection  on  Sir  John's  accuracy  to  point 
out  that  the  "  Crab  Nebula  "  in  Taurus  is  an  exception  to 
the  above  rule. 

Respecting  the  cluster  surrounding  co  Centauri,  Sir  John 
Herschel  says  that  "  it  is  visible  to  the  naked  eye  as  a  dim, 
round,  cometic  object  about  equal  to  a  star  of  4^  magni- 
tude, though  probably  if  concentrated  in  a  single  point  the 
impression  on  the  eye  would  be  much  greater.  Viewed 
in  a  powerful  telescope  it  appears  as  a  globe  of  fully  20' 
in  diameter,  very  gradually  increasing  in  brightness  to  the 
centre,  and  composed  of  innumerable  stars  of  the  13th 


112  THE  STORY  OF  THE  STARS. 

and  15th  magnitudes,  the  former  probably  being  two  or 
more  of  tlie  latter  closely  juxtaposed." 

This  chapter  may  appropriately  be  concluded  with  a 
mention  of  some  large  clusters  not  specifically  globular  in 
form.  67  M.  Cancri  is  a  rich  but  loose  cluster  at  the  root 
of  the  Crab's  southern  claw.  Smyth  noted  it  as  consist- 
ing principally  of  a  mass  of  stars  of  the  9th  and  loth  mag- 
nitudes, gathered  somewhat  in  the  form  of  a  Phrygian 


Fig.  16.— 67  M.  CancrL 

cap,  followed  by  a  crescent  of  stragglers.  W.  Herschel 
saw  above  200  stars  at  once  in  the  field  of  view.  This  ob- 
ject precedes  a  Cancri  by  about  2°. 

77  M.  Ceti  is  a  round  stellar  object  near  ( in  the  con- 
stellation named.  It  is  small,  bright,  and  exactly  on  a 
line  with  3  small  stars,  one  preceding  and  2  following ;  of 
which  the  nearest  and  largest  is  of  the  9th  magnitude. 


CLUSTERS  OF  STARS. 


113 


Sir  W.  Herschel  made  this  object  a  peg  on  which  to  hang 
the  following  remark  :— "  We  may  conclude  that  the  pro- 
fundity of  the  nearest  part  is  at  least  of  the  910th  order." 
By  this  Sir  William  meant  that  this  object  is  910  times  as 


Fig.  17. — 77  M.  Ceti  (nebulous  star). 

far  off  as  stars  of  the  first  magnitude  ;  but.  to  say  the 
least  of  it,  this  is  a  highly  imaginative  thought — one  of  a 
type  which  I  think  is  too  common — and  rather  apt  to 
make  astronomy  and  astronomers  look  ridiculous  in  the 
minds  of  matter-of-fact  people. 

The  cluster  1 1  M.  AntinoT  is  an  interesting  cluster  of 
uncommon  form.  Smyth  likened  it  to  a  flight  of  wild 
ducks,  a  simile  more  appropriate  than  many  of  those  met 
with  in  astronomical  writings.  There  is  an  8th  magni- 
tude star  in  the  middle,  and  two  outside  its  limits  and 
preceding  it.  Smyth  remarks  : — "  By  all  analogy  these 
are  decidedly  between  us  and  the  cluster."     This,  how- 


114  THE  STORY  OF  THE  STARS. 

ever  was  not  the  opinion  of  Kirch,  its  discoverer,  who,  in 
1 68 1,  described  it  as  a  small,  obscure  spot,  with  a  star 
shining  through  and  rendering  it  more  luminous. 

In  the  field  with,  and  adjacent  to,  the  star  k  Crucis 
there  is  a  large  and  loose  cluster,  described  by  Sir  John 
Herschel  as  one  of  the  most  beautiful  objects  of  its  class. 
It  comprises  more  than  loo  stars  from  the  7th  magnitude 
downwards,  8  of  the  more  conspicuous  of  them  being 
coloured  various  shades  of  red,  green,  and  blue.  This 
object  was  very  carefully  surveyed  in  1872  by  Russell  at 
Sydney,  who  remarked  that  many  of  the  stars  had  drifted 
(presumably  in  consequence  of  proper  motion)  in  the  40 
years  which  had  elapsed  since  Sir  John's  drawing  was 
made.  Russell  adds  : — "  The  colours  of  this  cluster  are 
very  beautiful,  and  fully  justify  Herschel's  remark  that  it 
looks  like  a  '  superb  piece  of  fancy  jewellery.'  " 


CHAPTER   XVI. 

NEBULA. 

In  the  present  chapter  we  shall  consider  the  Nebulae 
commonly  so  called — those  celestial  objects  of  very  diverse 
sizes,  shapes,  and  brilliancy,  of  which  many  or  most  are 
probably  stellar  in  their  constitution,  though  some  of 
them,  however,  may  be  not  such  but  gaseous.  At  the 
outset  I  will  deal  with  them  merely  descriptively.  Mes- 
sier's  catalogue,  to  which  such  frequent  allusions  have 
been  made,  embracing  as  it  did  only  those  larger  and 
brighter  objects  which  were  within  reach  of  a  mere  hand 
telescope,  does  in  no  way  indicate  the  present  state  of  our 
knowledge  respecting  the  nebulae.  The  bulk  of  the  ob- 
jects enrolled  by  Messier  eventually  proved  to  be  resolvable 
star  clusters,  though  a  residue  were  veritable  nebulae^ 


NEBULA.  115 

faint,  misty  objects,  many  of  them  not  unlike  specks  of 
luminous  fog.  Of  these  nebulae  some  have  yielded  to  the 
larger  telescopes  of  modciu  days,  and  have  proved  to  be 
masses  of  stars  too  closely  aggregated  together  to  be  re- 
solved by  the  puny  telescopes  which  only  were  available  a 
century  or  more  ago.  Since  Messier's  days,  and  as  a  re- 
sult of  so  many  large  telescopes  having  been  set  to  work 
during  the  second  half  of  the  nineteenth  century,  the  num- 
ber of  observed  nebulae  has  become  so  great  that  upwards 
of  8000  are  now  on  record.  By  far  the  greater  number  of 
these  are,  however,  irresolvable,  and  therefore  it  is  an 
open  question  what  they  are. 

The  nebulae  generally  may  be  conveniently  classified 
under  six  general  heads,  it  being  understood  of  course 
that  this  classification  only  has  regard  to  form  or  size : — 
(i)  Annular  nebulae;  (2)  elliptic  nebulae  ;  (3)  spiral  nebu- 
lae; (4)  planetary  nebulae;  (5)  nebulous  stars;  (6)  large 
nebula  of  irregular  form. 

The  annular  nebulas  hitherto  recognised  scarcely  num- 
ber a  dozen,  and  of  these  one  only  is  large  or  bright 
enough  to  have  obtained  much  notoriety.  This  is  Mes- 
sier's 57th  in  the  constellation  Lyra.  If  it  be  realised  that 
the  word  "annular"  is  derived  from  the  Latin  word  an- 
nulus,  a  ring,  a  ready  clue  will  be  had  as  to  the  general 
form  of  these  bodies.  The  annexed  engraving  indicates 
it,  but  only  that  simple  conception  which  is  obtainable  by 
means  of  a  moderate-sized  telescope — say  an  instrument 
of  4  inches  aperture.  With  instruments  of  much  larger 
size  the  individuality  of  the  ring  disappears,  and  the  cen- 
tral space,  black  or  nearly  so  in  a  small  telescope,  shows 
evident  indications  of  nebulous  matter,  which  Lord  Rosse 
found  to  be  distributed,  not  uniformly,  but  in  streaks  ; 
whilst  the  external  edge  of  the  ring  was  broken  by  pro- 
jections of  various  sizes  and  shapes.  All  these  particulars 
will  be  better  understood  from  a  picture  than  from  any 


Il6  THE  STORY  OF  THE  STARS. 

written  description.  There  is  considerable  conflict  of 
opinion  as  to  the  ultimate  account  which  ought  to  be  ren- 
dered of  this  object  when  the  largest  available  telescopes 


Fig.  i8. — The  ring  nebula  in  Fig.  19.— The  ring  nebula  in 

Lyra.     {SirJ.Herschel.)  Lyra.     {Earl  0/ Rosse.') 


are  brought  to  bear  upon  it ;  Rosse,  Chacornac,  and 
Secchi  all  claimed  to  have  resolved  it  into  stars.  Hug- 
gins,  on  the  other  hand,  insists  that  it  is  merely  a  mass  of 
glowing  gas.  The  Lick  observers  find  its  structure  to  be 
very  complex,  but  seem  unwilling  to  commit  themselves 
to  a  very  definite  opinion  on  the  subject.  At  the  same 
time  they  make  mention  of  the  existence  of,  and  describe 
the  position  of,  numerous  individual  stars. 

Elliptic  nebulae  of  various  degrees  of  eccentricity,  from 
a  common  oval  to  a  long  streak,  are  met  with  in  various 
parts  of  the  heavens.  As  a  rule  they  are  very  bright,  and 
several  of  them  are  remarkable  as  having  double  stars  at 
or  near  each  of  their  foci.  There  is  one  elliptic  nebula 
which  stands  out  beyond  all  the  rest,  yet  its  great  size, 
brilliancy,  and  peculiar  features  forbid  its  being  regarded 
as  a  typical  elliptic  nebulae.  I  am  here  alluding  to  the 
"Great  Nebulae  in  Andromeda,"  Messier's  31st.  Its  ellip- 
ticity  is  considerable  ;  it  is  likewise  very  long,  and  has  a 
bright  central  condensation  which  renders  it  readily  dis- 


NEBULA.  117 

coverable  by  the  naked  eye  on  a  clear  night  not  far  from 
the  star  rj  Andromeda  of  magnitude  4^.  Sir  John  Her- 
schel's  drawing  is  well  known,  having  obtained  wide  cir- 
culation through  his  own  and  other  people's  books.  G. 
P.  Bond  was  the  first  to  improve  upon  it,  which  he  did 
when  he  published,  more  than  40  years  ago,  an  engraving 
exhibiting  much  more  internal  detail  than  Herschel  had 
shown.  In  particular  two  curious  black  streaks  or  longi- 
tudmal  vacuities,  which  run  nearly  parallel  to  the  major 
axis  of  the  oval  on  the  south  side.  Bond  traced  the  neb- 
ula to  a  length  of  4°  and  a  breadth  of  2^°. 

Roberts  (see  Frontispiece)  has  carried  the  matter  still 
further  than  Bond  had  done,  for  he  finds  traces  of  a  dark 
ring  separating  the  central  parts  of  the  nebula  from  an 
outer  brighter  portion,  the  whole  yield- 
ing traces  of  what  may  indicate  a 
spiral  structure.  No  telescope  has 
yet  resolved  this  object  distinctly  into 
stars,  though  several  hundred  stars 
have  been  counted  within  its  limits. 
This  object  is,  how^ever,  probably 
stellar,  and  may  one  day  be  proved  to 
be  such;  certain  is  it  that  it  is  not  Fig.  20.  — The  neb- 
gaseous.  The  other  extreme  of  ellip-  "  ^  4"!  W  I.  Vir- 
tic  nebula  is  illustrated  in  Fig.  20, 
which  represents  43  IJI  I.  Virginis,  a  long,  narrow  wisp 
of  luminous  matter  with  a  slight  condensation  m  the 
centre. 

"Spiral,"  or,  as  they  are  sometimes  called,  "Whirl- 
pool "  nebulse  first  had  that  special  feature  of  them  brought 
out  by  the  late  Earl  of  Rosse.  The  best  known  is  Mes- 
sier's  51st  in  the  constellation  Canes  Venatici.  To  Sir  J. 
Herschel  it  presented  the  appearance  of  a  bright  globular 
cluster  encompassed  at  some  distance  by  a  bright  nebu- 
lous ring,  which  varied  very  much  in  brightness  in  its 


11,8 


THE   STORY   OF   THE   STARS. 


different  parts.  It  seemed  as  if  it  was  split  through  for 
about  fths  of  its  circumference  into  2  laminse,  one  ol 
which  gave  the  impression  that  it  was  turned  up  towards 
the  eye,  out  of  the  general  plane.     Sir  John  saw,  seem 


Fig.  21.— The  spiral  nebula  51  M.  Canum  Venaticorum. 
{Sir  J.  Herschel.) 

ingly  detached  from  the  main  object,  a  small,  bright, 
round  nebula.  Lord  Rosse's  telescope  entirely  altered 
the  aspect  of  the  whole  group.  The  ring  w^as  found  to 
pass  into  a  distinct  spiral  coil  of  nebulous  matter,  and  the 
outlying  portion  to  be  connected  with  the  main  mass  by 


NEBULA.  119 

a  curved  band,  the  whole  showing  indications  of  resolvabil- 
ity  into  stars.  No  ordinary  telescope  affords  even  suspicion 
of  these  details.  The  spectrum  appears  to  be  non-gaseous 
"  Planetary  "  nebulas  are  objects  first  so  designated  by 
Sir  W.  Herschel  because  they  exhibited  a  fairly  well  defined 
outline  as  of  a  disc,  circular  or  slightly  oval.     The  most 


fiG.  22. — The  spiral  nebula  51  M.  Canum  Venaticorum.     {Earl  0/ Rosse.) 

Striking  of  these  is  Messier's  97th  in  Ursa  Major,  2°  south 
ana  following  the  star /3.  It  has  been  described  as  "a 
very  singular  object,  circular  and  uniform,  and  after  a  long 
inspection  looks  like  a  condensed  mass  of  attenuated  light." 
It  has  a  diameter  of  2'  40".  The  late  Earl  of  Rosse  de- 
tected perforations  and  a  spiral  tendency  in  it.     He  found 


I20 


THE  STORY  OF  THE  STARS. 


Fig.  23— The  "  Owl  "  nebula 
in  Ursa  Major. 


a  Star  in  about  the  centre  of  each  main  perforation  and 
called  it  the  "  Owl  "  nebula,  from  its  appearance.  One  of 
the  stars  seems  to  have  disap- 
peared since  1850,  or,  as  a 
thoughtful  writer  suggests,  the 
owl  has  closed  one  of  his  eyes  ! 
Huggins  has  found  the  spec- 
trum gaseous. 

The  planetary  nebulae  are 
not  very  numerous  and  not  very 
bright,  which  is  a  matter  for  re- 
gret, because  it  would  seem  that 
they  possess  interesting  features 
entitling  them  to  the  special  at- 
tention of  astronomers  but  needing  large  telescopes.  For 
instance,  there  is  one  in  the  constellation  Draco,  No. 
37  in  Sir  W.  Herschel's  IVth  class,  which,  according 
to  Professor  Holden,  who  has  studied  it  with  the  Lick 
telescope,  possesses  an  extraordinary  structure.  He  says 
that  it  "  is  apparently  composed  of  rings  overlying  each 
other,  and  it  is  difficult  to  resist  the  conviction  that  these 
are  arranged  in  space  in  the  form  of  a  true  helix."  At 
the  first  glance  the  nebula  appears  to  Holden  to  consist 
of  2  circles  which  intersect,  a  central  star  being  within 
the  area,  resulting  from  the  intersection  of  the  2  circles. 
At  the  S.  point  of  intersection  the  brightness  is  ap- 
proximately twice  the  average  brightness  of  the  circum- 
ference ;  at  the  N.  point  it  is  less  bright  relatively.  A 
little  attention,  however,  seems  to  show  that  these  rings 
are  so  arranged  that  one  complete  ring  lies  on  the  upper 
or  hither  side  (nearer  the  eye)  of  the  other  complete  ring 
which  is  undermost  or  farther  from  the  eye.  There  is 
another  peculiar  feature.  The  nebula  itself  is  unmistak- 
ably blue  in  colour,  whilst  the  star  is  yellowish-red.  Star 
and  nebula  yield  different  spectra,  and  require  for  accu- 


NEBULiE.  1 2 1 

rate  definition  the  telescope  to  be  brought  to  a  different 
focus  according  as  it  is  desired  to  obtain  a  good  image 
of  the  one  or  the  other.  All  these  facts  point  to  remark- 
able intrinsic  peculiarities  in  this  object.  Holden  finds 
the  nebula  i  J§i  IV.  Aquarii  to  possess  some  analogies 
with  the  nebula  in  Draco  just  described. 

Before  passing  away  from  the  planetary  nebulas  some 
further  peculiarities  appertaining  to  them  deserve  a  pass- 
ing notice.  According  to  the  spectroscope,  they  are  most- 
ly gaseous,  and  several  are  noticeably  bluish  in  hue. 
Three  fourths  of  them  are  in  the  southern  hemisphere, 
and  the  greater  number  are  in,  or  ver}'  close  to,  the  Milky 
Way. 

"Nebulous  stars,"  according  to  their  name,  are  ordi- 
nary stars  with  a  faint  nebulosity  surrounding  them  ;  but 
the  term  does  not  seem  altogether  a  happy  one.  Hind 
remarks  that  the  nebulosity  is  in  some  cases  well  defined, 
but  in  other  cases  is  quite  the  reverse ;  that  "  the  stars 
thus  attended  have  nothing  in  their  appearance  to  dis- 
tinguish them  from  others  entirely  destitute  of  such  ap- 
pendages ;  nor  does  the  nebulous  matter  in  which  they 
are  situated  offer  the  slightest  indication  of  resolvability 
into  stars  with  any  telescopes  hitherto  constructed." 

Perhaps  the  most  striking  nebulous  star  is  No.  45  in 
Sir  W.  Herschel's  IVth  class,  in  the  constellation  Gemini. 
Sir  Jchn  Herschel  speaks  of  it  as  an  8th  magnitude  star 
which  lies  "exactly  in  the  centre  of  an  exactly  round, 
bright  atmosphere  25"  in  diameter."  Key  described  it  as 
"  a  bright  but  somewhat  nebulous  star  closely  surrounded 
by  a  dark  ring;  this  again  by  a  luminous  ring;  then  an 
interval  much  less  luminous,  and;  finally,  at  some  distance 
an  exterior  luminous  ring."  This  description  accords  well 
with  the  late  Earl  of  Rosse's. 

The  brightest  nebulous  star  certainly  recognised  as 
such  appears  to  be   i  Orionis,  a  triple  star  of  mag.   3-^. 


122  THE  STORY  OF  THE  STARS. 

€  Orionis,  of  mag.  2^,  is  often  spoken  of  as  a  star  sur- 
rounded by  a  nebulosity,  but  the  evidence  is  very  contra- 
dictory, and  inclines  on  the  whole  to  the  negative. 

The  last  class  of  nebulas  remaining  to  be  described 
are  some  of  very  diverse  size  and  shape,  which  cannot  be 
brought  under  any  general  denomination. 

The  "  Crab  nebula  "  in  Taurus  bears  a  popular  and 
familiar  designation,  but  it  does  not  seem  to  rest  on  a 
very  satisfactory  foundation.  In  all  ordinary  telescopes 
this  object  exhibits  a  simple  oval  outline,  but  the  special 
title  was  based  on  the  late  Lord  Rosse's  early  description 
of  it,  which  Sir  John  Herschel  thought  justified  by  the 
facts,  though  the  later  Parsonstown  observations  seem  to 
negative  the  claw  features.  It  was  the  discovery  of  this 
object  in  1758,  when  he  was  following  a  comet,  which  led 
Messier  to  form  his  well-known  catalogue  of  nebulas. 

All  things  considered,  it  seems  probable  that  the 
"Great  Nebula  in  Orion"  must  be  regarded  as  the 
grandest  and  most  interesting  of  all  the  nebulse.  I  have 
in  a  previous  chapter  mentioned  it  in  connection  with  the 
multiple  star  B  Orionis,  which  it  surrounds ;  and  the  dia- 
gram already  given,  rough  though  it  is,  affords  an  idea  of 
the  prominent  feature  of  the  nebula  which  presents  itself 
in  every  small  telescope,  namely,  the  "  Fish's  mouth." 
Sir  John  Herschel's  general  description,  written  a  great 
many  years  ago,  still  in  the  main  holds  good,  though 
modern  observations,  when  made  with  the  large  tele- 
scopes of  the  present  day,  bring  out  many  features  not 
recognised  half  a  century  ago  ;  and  in  particular  exhibit 
very  distinctly  what  may  be  called  the  flocculent  charac- 
ter or  structure  of  the  nebula. 

Sir  John  Herschel's  account  runs  as  follows  : — "  In  its 
more  prominent  details  may  be  traced  some  slight  resem- 
blance to  the  wings  of  a  bird.  In  the  brightest  portion 
are  four  conspicuous  stars,  forming  a  trapezium.     The 


NEBULA.  123 

nebulosity  in  the  immediate  vicinity  of  these  stars  is  floc- 
culent  and  of  a  greenish-white  tinge;  about  half  a  degree 
northward  of  the  trapezium  are  2  stars  involved  in  a 
branching  nebula  of  singular  form,  and  southward  is  the 
star  I  Orionis,  also  situated  in  a  nebula.  Careful  exam- 
ination with  powerful  telescopes  has  traced  out  a  conti- 
nuity of  nebulous  light  between  the  great  nebula  and  both 
these  objects,  and  there  can  be  but  httle  doubt  that  the 
nebulous  region  extends  northwards  as  far  as  in  e  the  belt 
of  Orion,  which  is  involved  in  a  strong  nebulosity,  as  well 
as  several  smaller  stars  in  the  immediate  neighbourhood." 

Secchi  thought  that  this  nebula  must  be  considered  as 
extending  far  beyond  the  limits  usually  assigned  to  it,  and 
that  there  exist  in  various  directions,  and  remote  from  the 
principal  centre,  scattered  fragments  of  nebulous  matter 
which  all  really  belong  to  the  main  mass.  He  ascribed  to 
the  whole,  speaking  roughly,  a  triangular  outline  with  a 
base  of  4°  and  a  height  of  about  5^°,  reaching  downward, 
from  ^  in  Apex  (with  a  break,  however,  at  cr)  almost  as 
far  as  e.  Photographic  and  spectroscopic  observations 
have  been  carried  out  on  a  considerable  scale  of  late  years. 
The  latter  are  thought  to  indicate  that  the  nebula  consists 
of  incandescent  hydrogen  gas.  The  multiplication  of  pho- 
tographs spread  over  a  term  of  years  may  lead  to  a  better 
understanding  of  the  circumstances  and  conditions  of  this 
nebula  than  is  at  present  possible.  The  existing  drawings 
of  it,  extending  over  nearly  a  century,  are  so  much  want- 
ing in  consistency  one  with  another  as  to  have  led  many 
persons  to  surmise  that  it  has  undergone  distinct  change, 
but  the  evidence  to  support  this  theory  falls  far  short  of 
what  is  necessary  to  sustain  such  a  suggestion. 

30  Doradus  is  a  nebula  in  the  Southern  hemisphere 
which,  from  Sir  John  Herschel's  description  and  engraving 
of  it,  must  be  a  very  remarkable  object.  Sir  John  speaks 
of  it  as  "  one  of  the  most  singular  and  extraordinary  ob- 


124  THE  STORY  OF  THE  STARS. 

jects  which  the  heavens  present."  Strange  to  say,  he 
does  not  describe  it  in  detail,  contenting  himself  by  saying 
that  the  engraving  (in  his  Outlines  of  Astronomy)  is  so 
satisfactory  as  to  render  further  description  superfluous. 
The  special  feature  of  this  nebula  is  the  v^^onderful  series 
of  convolutions  which  it  exhibits— masses  of  nebulous 
matter  twisted  in  and  out  in  singular  fashion  with  num- 
berless black,  or  more  or  less  starless,  interstices. 

Another  Southern  nebula  not  entirely  unlike  the  fore- 
going is  that  surrounding  the  strange  variable  star  7^  Ar- 
gus already  described.  Sir  John  Herschel's  account  of  it, 
penned  at  the  Cape  of  Good  Hope  some  60  years  ago, 
runs  as  follows  :—"  Viewed  with  an  18-inch  reflector,  no 
part  of  this  strange  object  shows  any  sign  of  resolution 
into  stars,  nor  in  the  brightest  and  most  condensed  por- 
tion, adjacent  to  the  singular  oval  vacancy  in  the  middle 
of  the  figure,  is  there  any  of  that  curdled  appearance,  or 
that  tendency  to  break  up  into  bright  knots  with  interven- 
ing darker  portions,  which  characterise  the  nebula  of 
Orion,  and  indicate  its  resolvability.  ...  It  is  not  easy  for 
language  to  convey  a  full  impression  of  the  beauty  and 
sublimity  of  the  spectacle  which  this  nebula  offers,  as  it 
enters  the  field  of  the  telescope  (fixed  in  R.  A.)  by  the 
diurnal  motion,  ushered  in  as  it  is  by  so  glorious  and  in- 
numerable a  procession  of  stars,  to  which  it  forms  a  sort 
of  climax." 

Some  mystery  hangs  over  this  nebula  and  its  central 
Stat  Much  excitement  was  caused  in  1863  by  the  publi- 
cation of  an  announcement  by  Abbott,  of  Hobart  Town, 
Tasmania,  that,  whereas  Sir  John  Herschel  had  noticed 
near  the  centre  of  the  nebula  a  lenticular  sort  of  space  de- 
void of  stars,  7)  being  some  distance  from  this  void  and 
closely  encompassed  by  nebulous  matter,  the  void  space 
had  altered  in  form,  and  the  star  (which  had  dwindled 
down  to  the  6th  mag.)  no  longer  had  nebulous  matter 


NEBULA.  125 

.  /ose  up  to  it.  These  assertions,  indicative,  if  true,  of  ma- 
terial clianges  in  the  appearance  of  the  nebulas  having 
taken  place  between  1883  and  1863,  were  reviewed  by- 
Captain  J.  Herschel,  in  India,  and  Dr.  B.  A.  Gould,  in 
South  America,  and  others,  and  the  general  verdict  was 
that  the  allegations  of  Abbott  were  unfounded,  and  that 
Sir  John  Herschel's  drawing  of  1833  continued  in  1882  to 
represent  the  details  of  the  nebula  as  they  were  to  be  seen 
at  the  later  date. 

The  constellation  Sagittarius  contains  2  large  nebulous 
masses  of  considerable  interest  at  no  great  distance  from 
each  other.  20  M.  Sagittarii  is  the  chief  member  of  an 
important  group  respecting  which  Sir  John  Herschel 
writes  as  follows  : — "  One  of  them  is  singularly  trifid,  con- 
sisting of  3  bright  and  irregularly  formed  nebulous  masses, 
graduating  away  insensibly  externally,  but  coming  up  to  a 
great  intensity  of  light  at  their  anterior  edges,  where  they 
enclose  and  surround  a  sort  of  three-forked  rift  or  vacant 
area,  abruptly  and  uncouthly  crooked,  and  quite  void  of 
nebulous  light.  A  beautiful  triple  star  is  situated  precisely 
on  the  edge  of  one  of  these  nebulous  masses,  just  where 
the  interior  vacancy  forks  out  into  two  channels." 

8  M.  Sagittarii,  not  far  from  the  last  named,  is  another 
remarkable  object,  perceptible  to  the  naked  eye,  and  show- 
ing effectively,  even  in  a  telescope  as  small  as  a  3-inch. 
Sir  John  Herschel  thus  speaks  of  it : — "  A  collection  of 
nebulous  folds  and  masses,  surrounding  and  including  a 
number  of  oval  dark  vacancies,  and  in  one  place  coming 
up  to  so  great  a  degree  of  brightness  as  to  offer  the  ap- 
pearance of  an  elongated  nucleus.  Superposed  upon  this 
nebula,  and  extending  in  one  direction  beyond  its  area,  is 
a  fine  and  rich  cluster  of  scattered  stars,  which  seem  to 
have  no  connection  with  it  as  the  nebula  does  not,  as  in 
the  region  of  Orion,  show  any  tendency  to  congregate 
about  the  stars." 


126  THE  STORY  OF  THE  STARS. 

The  small  constellation  Scutum  Sobieskii  contains  a 
rather  famous  object  sometimes  (but  not  very  judiciously) 


Fig.  24. — The  "  Omega"  nebula  in  Scutum  Sobieskii. 

called  the  "Horse-shoe"  nebula,  or  by  others- (and  with 
more  propriety)  the  "  Omega  "  nebula.  From  the  engrav- 
ing annexed  it  will  be  seen  that,  as  regards  at  any  rate  a 
small  telescope,  the  idea  conveyed  is  more  that  of  a  swan 
as  seen  floating  on  the  surface  of  water.  As  in  the  case 
of  7]  Argus,  allegations  have  been  made,  and  apparently 
with  better  foundation  in  this  case,  that  important  changes 
have  taken  place  in  the  appearance  of  this  nebula  since  the 
first  drawings  of  it  were  made.  Weighty  names  are  at- 
tached to  these  conclusions,  and  Holden,  who  has  investi- 
gated with  much  care  and  detail  its  history,  as  recorded 
between  1833  and  1875,  concludes  that  "the  'Horse-shoe' 
has  moved  with  reference  to  the  stars,"  and  that  therefore 
"  we  have  evidences  of  a  change  going  on  in  the  nebula. 
This  may  be  a  veritable  change  in  the  structure  of  the  neb- 
ula itself,  such  as  was  suspected  by  Schroter,  confirmed 
by  O.  Stuve,  and  again  confirmed  by  myself  in  the  nebula 


NEBULA.  127 

of  Orion  ;  or  it  may  be  the  bodily  shifting  of  the  whole 
nebula  in  space." 

The  "Dumb-bell"  Nebula  (27  M.  Vulpeculae)  is  too 
well  known  to  need  a  lengthened  description  in  this  place. 
The  records  of  its  appearance  during  more  than  a  century 
past,  as  telescopes  of  successively  increasing  power  have 
been  brought  to  bear  on  it,  constitute  a  weighty  warn- 
ing to  those  who,  on  the  strength  of  seeming  discrepancies 
in  verbal  descriptions  and  drawings,  choose  to  infer  that 
absolute  changes  have  taken  place  in  the  appearance  or 
circumstances  of  celestial  objects.  It  is  not  too  much  to 
say  that  whilst  the  designation  "  Dumb-bell  "  is  fairly  ap^ 
propriate  in  describing  this  object  as  seen  in  telescopes 
up  to  6  or  8  or  more  inches  of  aperture,  yet  this  feature 
becomes  inappreciable  altogether  in  the  giant  telescopes 
of  the  present  day,  which  run  to  20,  or  30,  or  40  inches  of 
aperture.  Roberts's  photograph  of  this  object  is  visually 
almost  irreconcilable  with  the  older  drawings,  in  which 
the  "  Dumb-bell  "  idea  is  the  dominant  one. 

The  Southern  hemisphere  contains  two  objects  which 
must  not  be  passed  over  in  treating  of  nebulae.  These 
are  the  "  Magellanic  Clouds,"  or  the  "  Nubecula  Major  " 
and  **  Nubecula  Minor  " — both  of  them  terms  recalling  the 
cloudlike  appearance  of  these  objects,  the  words  "major" 
and  "  minor  "  relating  of  course  to  their  size.  Both  are 
at  no  great  distance  from  the  Pole,  the  "  Greater  Cloud  " 
being  in  the  constellation  Dorado,  and  the  "  Lesser 
Cloud  "  in  Toucan.  They  are  of  a  somewhat  oval  shape 
and  visible  to  the  naked  eye,  but  the  smaller  one  disap- 
pears in  strong  moonlight.  Sir  John  Herschel  describes 
them  as  consisting  of  swarms  of  stars,  clusters,  and 
nebulae. 

The  distribution  of  the  nebulae  in  the  heavens  is  a  sub- 
ject which  has  attracted  the  attention  of  many  astrono- 
mers who  have  had  theories  to  advance  respecting  such 


128  THE   STORY  OF   THE   STARS. 

topics,  or  who  have  written  on  the  constitution  of  the 
Universe.  But  I  do  not  know  that  it  can  be  said  that 
very  much  light  has  been  thrown  upon  the  questions  of 
this  character  which  have  presented  themselves  for  solu- 
tion. One  thing  is  very  noteworthy,  and  no  doubt  is  sig- 
nificant, but  we  do  not  know  of  what  it  is  significant.  The 
distribution  of  the  nebulae  over  the  heavens  is  extremely 
unequal.  They  congregate  in  a  zone  which  crosses  the 
Milky  Way  at  right  angles.  The  majority  are  to  be 
found  in  a  zone  which  scarcely  embraces  an  eighth  part 
of  the  heavens.  The  constellation  Virgo  is  where  they 
are  gathered  together  in  greatest  number,  and  they  abound 
also  in  the  neighbouring  constellations  of  Leo,  Ursa 
Major,  Camelopardus,  Draco,  Bootes,  Coma  Berenices, 
and  Canes  Venatici.  In  the  part  of  the  heavens  almost 
exactly  opposite  to  these  constellations — that  is  to  say,  in 
Pegasus,  Andromeda,  and  Pisces — they  are  also  numer- 
ous. The  inequality  in  the  distribution  of  the  nebulas 
will  perhaps  be  best  brought  home  to  the  reader  by  con- 
sidering how  they  are  distributed  in  hours  of  Right  As- 
cension. Of  the  5079  clusters  and  nebulae  entered  in  Sir 
John  Herschel's  Catalogue  of  1864  whilst  the  XlXth  and 
XXth  hours  contain  only  79  and  90  objects  respectively, 
the  Xlth  hour  contains  421  and  the  Xllth  686.  The 
last-named  hour  is  that  which  embraces  a  large  part  of 
Virgo.  The  regions  of  the  heavens  which  lie  nearest  to 
the  Milky  Way  are  the  poorest  in  nebulas,  while  they 
are  most  abundant  around  the  Poles  of  that  great  and 
mysterious  belt.  In  the  Southern  hemisphere  the  nebulae 
are  more  uniformly  spread  over  the  zone  which  surrounds 
the  South  Pole.  On  the  other  hand,  their  aggregate  num- 
ber is  smaller;  nevertheless  there  are  2  magnificent  re- 
gions there  which  alone  contain  nearly  400  nebulas  and 
star  clusters. 

It  is  a  remarkable  fact  that  almost  all  the  nebulae  in- 


THE  MILKY  WAY.  1 29 

dicated  by  the  spectroscope  to  be  gaseous  are  situated 
either  within  the  Milky  Way  or  closely  adjacent  thereto ; 
whilst  in  the  regions  near  the  poles  of  the  Milky  Way 
gaseous  nebulae  are  wanting,  though  other  nebulae  are 
abundant. 

The  reader  will  remember  what  has  already  been  said 
respecting  the  alleged  variability  of  great  nebula  in  Orion, 
of  the  nebula  surrounding  77  Argus,  and  of  the  "  Omega  " 
nebula  in  Vulpecula.  Subject  to  the  remarks  already 
made  in  dealing  with  those  3  nebulae,  it  is  to  be  consid- 
ered that,  though  there  are  such  things  as  variable  stars, 
no  variable  nebulas  are  known  to  exist. 


CHAPTER   XVII. 

THE   MILKY   WAY. 

Though  when  one  gazes  at  the  Milky  Way  there  is, 
in  a  certain  sense,  not  much  to  see  (or  at  least  not  much 
which  one  can  realise),  yet  an  attentive  consideration  of  it 
with  the  assistance  of  a  telescope  brings  to  light  a  vast 
variety  of  details  of  the  highest  interest.  How  it  pre- 
sented itself  to  our  English  forefathers  is  sufficiently 
shown  by  Milton's  well-known  description  of  it  {Paradise 
Lost,  bk.  vii.  v.  577-81)  as — 

"  A  broad  and  ample  road,  whose  dust  is  gold 
And  pavement  stars,  as  stars  to  thee  appear, — • 
Seen  in  the  Galaxy,  that  Milky  Way 
Which  nightly,  as  a  circling  zone,  thou  seest. 
Powdered  with  stars." 

From  the  foregoing  it  will  appear  that  Wordsworth 
was  not  displaying  his  own  original  genius  when  (in  Dion) 
he  spoke  of — 
9 


130  THE  STORY  OF  THE  STARS. 

*'  Heaven's  broad  causeway  paved  with  stars.'* 

Perhaps  before  I  recount  any  further  speculations  of 
this  character  we  had  better  consider  the  Milky  Way  de- 
scriptively. So  far  as  I  know  the  only  astronomer  who 
has  written  on  it,  and  been  able  to  do  so  from  personal 
study  of  it  in  both  hemispheres  of  the  earth,  is  Sir  John 
Herschel.  It  is  obvious  that  no  description  of  such  an 
object  can  be  adequately  framed  merely  by  the  colloca- 
tion of  accounts  prepared  piecemeal,  but  that  there  is  re- 
quired the  pen  of  a  man  who  has  taken  notes  of  it  at  first 
hand  round  its  entire  circumference.  I  make  no  apology, 
therefore,  for  borrowing,  in  a  simplified  and  condensed 
form.  Sir  John  Herschel's  description  of  the  Milky  Way. 

Following  the  line  of  its  greatest  brightness,  as  well  as 
its  varying  breadth  permits,  its  course  conforms  as  nearly 
as  may  be  to  that  of  a  great  circle  inclined  about  63°  to 
the  equinoctial,  and  cutting  that  circle  in  R.  A.  6h.  47m., 
and  i8h.  47m.,  so  that  its  poles  are  in  R.  A.  I2h.  47m., 
Deck  N.  27°  and  R.A.  oh.  47.,  Decl.  S.  27°.  Through, 
out  the  region  where  it  is  sub-divided  this  great  circle 
runs  as  it  were  in  between  the  2  great  streams  of  galaxy 
matter,  with  a  nearer  approximation,  however,  to  the 
brighter  and  continuous  stream.  If  we  trace  the  Milky 
Way  in  the  order  of  R.  A.,  we  find  it  traversing  Cassi- 
opeia, its  brighter  part  passing  about  2°  to  the  North  ot 
d.  Passing  thence  between  y  and  e  it  sends  off  a  branch, 
southwards  and  preceding,  towards  a  Persei,  conspicuous 
as  far  as  that  star,  prolonged  faintly  towards  e  Persei,  and 
possibly  traceable  towards  the  Hyades  and  Pleiades.  The 
main  stream,  however  (which  is  here  very  faint),  passes 
on  through  Auriga  over  e,  (,  rj,  preceding  Capella.  between 
the  feet  of  Gemini  and  the  horns  of  Taurus  (where  it  in- 
tersects the  ecliptic  nearly  in  the  solstitial  colure),  and 
thence  over  the  club  of  Orion  to  the  neck  of  Monoceros, 


THE  MILKY  WAY.  131 

intersecting  the  equinoctial  in  R.A.  6h.  54m.  Up  to  this 
point,  from  the  offshoot  in  Perseus,  its  light  is  feeble,  but 
thenceforward  it  gradually  brightens  up,  and  from  the 
shoulder  of  Monoceros  and  over  the  head  of  Canis  Major 
it  presents  a  broad,  moderately  bright,  very  uniform  and» 
to  the  naked  eye,  starless  stream  up  to  the  point  where  it 
enters  the  prow  of  Argo  nearly  on  the  Southern  Tropic. 
Here  it  again  subdivides  (about  the  star  m  Puppis),  send- 
ing off  a  narrow  and  winding  branch  on  the  preceding 
side  as  far  as  y  Argus,  where  it  abruptly  terminates. 

The  main  stream  pursues  its  southward  course  to  the- 
33rd  parallel  of  South  Declination,  where  it  diffuses  itself 
broadly  and  again  subdivides,  opening  out  into  a  wide 
fan-like  expanse,  nearly  20°  in  breadth,  formed  of  inter- 
lacing branches,  all  of  which  terminate  abruptly,  in  a  line 
drawn  nearly  through  X  and  y  Argus, 

Here  the  continuity  of  the  Milky  Way  is  interrupted 
by  a  wide  gap,  and  where  it  recommences  on  the  oppo- 
site side  it  is  by  a  somewhat  similar  fan-shaped  assem- 
blage of  branches  which  converge  upon  r\  Argils.  Thence 
it  crosses  the  hind  feet  of  the  Centaur,  forming  a  curious 
and  sharply  defined  semicircular  cavity,  and  enters  the 
Cross  by  a  bright  isthmus  not  more  than  3°  or  4°  wide — 
this  is  the  narrowest  portion  of  the  Milky  Way.  After 
this  it  immediately  expands  into  a  bright  mass,  enclosing 
a  and  /3  Crucis  and  jS  Centauri,  extending  almost  up  to 
a  Centauri.  In  the  midst  of  this  bright  mass,  and  occu- 
pying about  \  its  breadth,  occurs  a  singular  dark  pear- 
shaped  vacancy  about  8°  long  and  5°  broad,  very  con- 
spicuous, and  for  several  centuries  past  called  the  "  Coal- 
sack  " — a  name  given  to  it  by  the  early  navigators.  In 
this  vacancy  there  is  only  one  very  small  naked-eye  star, 
though  there  are  telescopic  stars.  The  striking  blackness 
is  the  effect  of  contrast  with  mass  of  bright  matter  by 
which  the  black  area  is  surrounded.     This  is  the  place  of 


132  THE  STORY  OF  THE  STARS. 

the  nearest  approach  of  the  Milky  Way  to  the  South 
Pole.  Throughout  all  this  region  its  brightness  is  very 
striking,  and  when  compared  with  the  more  Northern 
portion,  the  course  of  which  has  been  already  traced,  con- 
veys strongly  the  idea  of  greater  proximity,  and  would 
almost  lead  to  a  belief  that  our  situation  as  spectators  is 
separated  on  all  sides  by  a  considerable  interval  from  the 
dense  body  of  stars  composing  the  Galaxy,  which  in  this 
view  would  have  to  be  considered  as  a  flat  ring  of  im- 
mense and  irregular  breadth  and  thickness  within  which 
we  are  eccentrically  situated,  nearer  to  the  Southern  than 
to  the  Northern  part  of  its  circuit. 

At  a  Centauri  the  Milky  Way  again  subdivides,  send- 
ing off  a  great  branch  of  nearly  half  its  breadth,  but 
which  thins  off  rapidly,  at  an  angle  of  20°  with  its  gen- 
eral direction,  towards  the  preceding  side  to  rj  and  d  Lupi, 
beyond  which  it  loses  itself  in  a  narrow  and  faint  stream- 
let. The  main  stream  passes  on,  increasing  in  breadth, 
to  y  Normas,  where  it  makes  an  abrupt  elbow  and  again 
subdivides  into  one  principal  and  continuous  stream  of 
very  irregular  breadth  and  brightness  on  the  following 
side,  and  a  complicated  system  of  interlaced  streaks  and 
masses  on  the  preceding,  which  covers  the  tail  of  Scorpio, 
and  terminates  in  a  vast  and  faint  effusion  over  the  whole 
extensive  region  occupied  by  the  preceding  leg  of  Ophiu- 
chus,  extending  northwards  to  a  parallel  of  13°  of  South 
Declination,  beyond  which  it  cannot  be  traced,  a  wide  in- 
terval of  14°  free  from  all  appearance  of  nebulous  light 
separating  it  from  the  great  branch  on  the  North  side  of 
the  equinoctial  of  which  it  is  usually  represented  as  a  con- 
tinuation. 

Returning  to  the  point  of  separation  of  this  great 
branch  from  the  main  stream  at  a  Centauri,  let  us  now 
pursue  the  course  of  the  latter.  Making  an  abrupt  bend 
to  the  following  side  it  passes  over  t  Arse,  6  and  t  Scorpii, 


THE  MILKY  WAY.  I^^ 

and  7  Telescopii  to  y  Sagittarii,  where  it  suddenly  collects 
into  a  vivid  oval  mass  about  6°  in  length  and  4°  in  breadth, 
so  excessively  rich  in  stars  that  a  very  moderate  calcula- 
tion makes  their  number  exceed  100,000.  Northward  of 
this  mass  this  stream  crosses  the  ecliptic  in  longitude 
about  276°,  and  proceeding  along  the  bow  of  Sagittarius 
into  Antinoiis,  has  its  course  rippled  by  3  deep  concavi- 
ties separated  from  each  other  by  remarkable  protuber- 
ances, of  which  the  larger  and  brighter  (situated  between 
the  stars  3  and  6  Aquil^e)  forms  the  most  conspicuous 
patch  in  the  Southern  portion  of  the  Milky  Way  visible  in 
English  latitudes. 

Crossing  the  equinoctial  at  the  XlXth  hour  of  R.  A. 
it  runs  in  an  irregular,  patchy,  and  winding  stream  through 
Aquila,  Sagitta,  and  Vulpecula  up  to  Cygnus.  At  6  Cygni 
its  continuity  is  interrupted,  and  a  very  confused  and 
irregular  region  commences,  marked  by  a  broad,  dark 
vacuity  not  unlike  the  "  Coal-sack  "  of  the  Southern  hemi- 
sphere, occupying  the  space  between  e,  a  and  y  Cygni^ 
which  serves  as  a  kind  of  centre  from  which  3  great 
streams  diverge.  Of  these  streams  one  has  been  already 
traced ;  a  second,  which  is  a  continuation  of  the  first 
(across  the  interval)  from  a  Cygni  northwards,  between 
Lacerta  and  the  head  of  Cepheus  to  the  point  in  Cassio- 
peia, whence  we  set  out ;  and  a  third  branching  off  from 
y  Cygni,  very  vivid  and  conspicuous,  running  off  in  a 
southerly  direction  through  (3  Cygni  and  s  Aquilae,  almost 
to  the  equinoctial,  where  it  loses  itself  in  a  region  thinly 
sprinkled  with  stars,  where  in  some  maps  the  modern 
constellation  Taurus  Poniatowskii  is  placed.  This  is  the 
branch  which,  if  continued  across  the  equinoctial,  might 
be  supposed  to  unite  with  the  great  southern  effusion  in 
Ophiuchus  already  noticed.  A  considerable  offshoot  or 
protuberant  appendage  is  also  thrown  off  by  the  northern 
stream  from  the  head  of  Cepheus  directly  towards  the 


134  THE  STORY  OF  THE  STARS. 

Pole  occupying  the  greater  part  of  the  trapezium  formed 
by  a,  /3,  t  and  5  of  that  constellation. 

In  connection  with  the  Milky  Way  a  large  amount  of 
speculation  has  been  indulged  in,  but  as  Gore  well  re- 
marks : — "  Many  attempts  have  been  made  to  form  a  sat- 
isfactory theory  of  the  construction  of  the  Milky  Way,  but 
these  efforts  have  been  hitherto  attended  with  but  little  suc- 
cess. This  is  not  surprising,  as  the  problem  is  evidently 
one  of  great  difficulty."  Thomas  Wright,  of  Durham,  was 
the  first  modern  speculator.  He  started,  about  1734,  a 
theory  which,  in  a  more  matured  form  and  worked  out 
wdth  better  materials,  was  put  forward  by  Sir  W.  Herschel 
about  1784  and  became  widely  known  as  the  "Stratum 
theory  "  of  the  Milky  Way,  or,  as  some  have  called  it,  the 
"Cloven  disc  theory."  ,  Briefly,  his  idea  was  that  the  stars 
were  not  indifferently  scattered  through  the  heavens,  but 
were  rather  arranged  in  a  certain  definite  stratum,  com- 
prised between  2  plane  surfaces  parallel  to  and  near  each 
other  but  prolonged  to  immense  distances  in  every  direc- 
tion, the  thickness  of  which  stratum,  as  compared  with 
its  length  and  breadth,  was  inconsiderable ;  and  that  the 
Sun  occupies  a  place  somewhere  about  the  middle  of  its 
thickness,  and  near  the  point  where  it  subdivides  into  2 
principal  streams  inclined  to  each  other  at  a  small  angle. 
This  theory  is  not  accepted  in  the  present  day,*  and  other 
theories  have  been  put  forth.  Proctor,  whose  strong 
point  was  running  down  his  rivals,  suggested  that  the 
form  of  the  Milky  Way  was  that  of  a  spiral,  but  this  no- 
tion has  been  demoHshed  by  Sutton.  Gould  is  disposed 
to  consider  the  Milky  Way  to  be  "  the  resultant  of  two  or 

*  Proctor  asserted  that  it  was  even  given  up  by  its  author,  but 
Sir  John  Herschel,  writing  more  than  half  a  century  afterwards, 
reproduced  it  without  any  hint  that  it  had  been  abandoned  by  his 
father,  and  a  son  is  a  better  authority  as  to  his  father's  opinions 
than  a  mere  stranger,  as  Proctor  was. 


THE  MILKY  WAY.  I35 

more  superposed  galaxies,"  whatever  that  may  mean.  All 
things  considered,  Gore's  words  are  eminently  wise  : — 
"  The  Copernicus  of  the  sidereal  system  has  not  yet  ap- 
peared, and  it  may  be  many  years,  or  even  centuries,  be- 
fore this  great  problem  is  satisfactorily  solved."  In  point 
of  fact,  for  more  than  2000  years  astronomers  (and  others) 
have  been  speculating  as  to  the  origin  and  nature  of  the 
Milky  Way.  Metrodorus  considered  it  to  be  the  original 
course  of  the  Sun  abandoned  by  him  after  the  bloody 
banquet  of  Thyestes ;  others  thought  that  it  pointed  out 
the  place  of  Phaeton's  accident,  whilst  yet  another  class 
regarded  it  as  being  made  up  of  the  ears  of  corn  dropped 
by  Isis  in  her  flight  from  Typhon.  It  seems  hardly  con- 
sonant with  our  prosaic  nineteenth-century  thoughts  to 
transcribe  such  rubbish  as  this,  yet  these  and  kindred  fa- 
bles and  fancies  have  taken  deep  root  in  the  human  mind, 
though  probably  it  is  true  that  they  do  not  possess  the 
ascendancy  which  they  did  even  fifty  years  ago.  There 
were,  however,  others  of  the  ancients  who,  though  no 
doubt  painfully  ignorant  of  physical  science,  as  tested  by 
our  modern  standards,  and  impregnated  with  ideas  of  the 
most  ridiculous  and  fantastic  character,  did,  at  any  rate, 
do  their  best,  according  to  their  lights.  For  instance, 
when  Aristotle  imagmed  the  Milky  Way  to  be  the  result 
of  gaseous  exhalations  from  the  earth  which  were  set  on 
fire  in  the  sky,  who  shall  say  that  he  did  not  prefigure 
Muggins's  conclusion  that  certain  of  the  nebulas  are 
nought  else  but  blazing  masses  of  hydrogen  or  other  ter- 
restrial gases  ?  It  is  more  difficult,  however,  to  find  a 
modern  counterpart  for  the  idea  of  Theophrastus,  that  it 
is  the  soldering  together  of  2  hemispheres  ;  or  for  the  con- 
ception of  Diodorus,  that  in  gazing  at  the  Milky  Way  we 
see  a  dense  celestial  fire  which  shows  itself  through  the 
clefts  which  indicate  that  2  hemispheres  are  about  to  burst 
apart.     It  is,  however,  interesting  to  come  upon  specula- 


136  THE   STORY  OF  THE  STARS. 

tions  by  Democrates  and  Pythagoras  that  the  galaxy  was 
neither  more  nor  less  than  a  vast  assemblage  of  stars. 
Ovid  speaks  of  it  as  a  high-road  "  whose  groundwork  is 
stars."  Manilius,  who  posed  as  an  astronomical  writer 
about  the  first  century  of  the  Christian  Era,  and  who  was 
probably  a  Roman,  uses  similar  language.  In  a  poem 
which  he  wrote  called  the  "  Astronomicon,"  and  which 
has  been  more  than  once,  I  think,  rendered  into  English, 
we  find  the  following  allusion  to  the  Milky  Way : — 

"  Or  is  the  spacious  bend  serenely  bright 
From  little  stars,  which  there  their  beams  unite, 
And  make  one  solid  and  continued  light  ?  " 

It  is  not  a  little  curious  how  widely  spread,  both  as 
regards  time  and  place,  is  the  association  of  the  idea  of 
milk  with  the  Milky  Way  ;  and  though,  no  doubt,  it  may 
be  a  case  of  one  language  supplying  a  word  which  others 
borrowed  and  translated,  yet  this  would  hardly  have  been 
done  if  the  underlying  idea  had  not  proved  acceptable. 
The  Greek  name  was  VaXa^'ias  or  YmkKo^  yaXaKTLKos,  which 
the  Romans  converted  into  Circulus  Lacteus  or  Orbis 
Lacteus,  whence  no  doubt  our  "  Milky  Way."  At  the 
same  time  our  English  ancestors  had  several  independent 
names  of  their  own.  Amongst  these  were  "Jacob's  Lad- 
der," "  The  way  to  St.  James's,"  and  "  Watling  Street." 
The  existence  of  these  names  supplies  another  proof,  if 
one  were  wanted,  that  the  cardinal  facts  and  features  of  a 
science  like  astronomy  often  take  a  much  deeper  hold 
over  the  popular  mind  than  might  be  expected. 


APPLICATION  OF  SPECTROSCOPE  TO  STARS.  137 


CHAPTER   XVIII. 

THE    APPLICATION    OF    THE    SPECTROSCOPE    TO    THE 
STARS   AND    NEBULAE. 

The  subject  covered  by  the  above  heading  has  of  late 
years  grown  to  be  a  very  large  one,  and  it  will  only  be 
possible  to  exhibit  here  a  bare  outline.  The  spectroscope 
was  first  applied  to  the  stars  by  Fraunhofer  about  1814. 
His  apparatus  consisted  only  of  a  small  prism  placed  in 
front  of  the  object  glass  of  a  telescope  belonging  to  a 
theodolite.  The  intervention  of  the  prism  changed  the 
image  of  the  star  from  the  bright  point  which  it  showed 
when  viewed  by  the  telescope  alone,  into  a  narrow,  bright 
line  which  exhibited  all  the  colours  of  the  rainbow  in  their 
customary  order,  from  red  atone  end  to  blue  at  the  other. 
The  formation  of  the  spectrum,  as  this  many-coloured  line 
is  called,  is  easily  understood.  The  light  from  a  star  con- 
sists, not  of  rays  of  one  colour  alone,  but  of  rays  of  an 
infinite  number  of  different  colours.  These,  in  the  ordi- 
nary course  of  things,  follow  the  same  path,  enter  the 
telescope  together,  come  practically  to  the  same  focus,  or 
nearly  so,  and  produce  a  single  and  colourless  image  of 
the  star,  because  the  combination  of  all  the  different  col- 
ours yields  the  sensation  which  we  term  white  light.  But 
when  the  light  of  a  star  passes  through  a  prism  it  becomes 
bent  out  of  its  course,  and  the  several  different  colours  are 
each  differently  affected,  some  being  more  bent  from  the 
original  straight  line  than  others.  Each  separate  coloured 
ray  then  produces  a  separate  coloured  image  of  the  star, 
and  these  images  no  longer  converge  together  to  the  same 
point,  but  fall  into  position  side  by  side,  overlapping  each 
other. 

Fraunhofer  found,  however,  in  the  case  of  the  stars,  as 
he  had  previously  found  on  examining  the  light  of  the  sun. 


138  THE   STORY  OF  THE   STARS. 

that  the  spectra  of  the  stars  were  not  quite  complete,  and 
instead  of  the  coloured  Hne  being  absolutely  continuous 
from  the  red  end  to  the  violet  end,  it  was  interrupted  here 
and  there  by  narrow  dark  spaces.  These  spaces,  in  the 
case  of  the  planets  Mars  and  Venus,  corresponded  pre- 
cisely with  those  spaces  which  he  had  already  detected  in 
the  spectrum  of  the  sun,  and  this  was  natural,  since  the 
planets  only  reflect  to  us  the  light  which  they  receive  from 
the  sun.  But  the  gaps  or  dark  lines  in  the  spectra  of  dif- 
ferent stars  were  not  precisely  identical  with  those  to  be 
traced  in  the  solar  spectrum,  and,  moreover,  the  spectra 
of  different  stars  were  different. 

This  was  an  important  discovery,  for  it  proved  that  the 
source  and  cause  of  these  dark  lines  depended  on  the  sun 
or  on  the  various  stars  themselves,  as  the  case  might  be  ; 
and  was  not  due  to  anything  in  our  atmosphere,  or  in  ce- 
lestial space,  for  in  such  case  all  the  lines  would  have 
been  alike.  Certain  particular  lines  were  indeed  traced  to 
our  atmosphere  as  they  were  invariably  seen  in  the  spec- 
trum of  any  celestial  body  when  it  was  near  the  horizon, 
and  was  therefore  being  viewed  through  a  great  thickness 
of  terrestrial  atmosphere. 

Fraunhofer  did  not  arrive  at  any  explanation  of  the 
cause  of  these  lines,  and  a  generation  passed  away  before 
Kirchhoff,  in  1859,  proved  that  a  number  of  the  solar  lines 
were  due  to  the  presence  in  the  sun's  atmosphere  of  the 
glowing  vapours  of  various  metals,  of  which  sodium  and 
iron  seemed  to  be  the  chief. 

The  presence  of  a  pair  of  bright  lines  in  the  orange- 
yellow  portion  of  the  spectrum  of  a  candle  flame  had  long 
been  noticed.  It  had  been  proved  that  these  were  due  to 
sodium,  and  it  had  been  shown  that  they  corresponded 
precisely  in  position  to  a  pair  of  dark  lines  known  as  the 
D  lines  in  the  spectrum  of  the  sun.  Kirchhoff  succeeded 
in  showing  that  a  glowing  gas  which,  at  a  given  tempera- 


APPLICATION  OF  SPECTROSCOPE  TO  STARS,  1 39 

ture,  gives  off  light  of  a  particular  tint  (or  rather  of  a  par- 
ticular wave-length)  possesses  also  at  that  temperature  the 
power  of  absorbing  light  of  that  same  wave-length.  The 
surface  of  the  sun  (the  "  photosphere,"  as  it  is  technically 
called)  emits  light  of  every  colour,  but  superposed  on  it 
are  the  luminous  vapours  of  various  metals.  These  va- 
pours, could  we  but  see  them  alone,  would  give  us  only 
light  of  certain  particular  colours — their  spectra  would  be 
spectra  of  bright  lines.  But,  looking  through  them  at  the 
solar  photosphere  (which  lies  below  1,  these  gases  shut  off 
from  us  light  emanating  from  the  photosphere  of  precisely 
the  same  quality  as  they  themselves  emit.  We  find, 
therefore,  the  solar  spectrum  crossed  by  dark  lines,  which 
correspond  to  the  bright  lines  of  the  gases  of  the  solar  at- 
mosphere. The  conclusion  of  the  whole  matter  is  that 
whilst  the  two  D  lines  show  the  presence  of  sodium,  other 
lines,  known  as  C,  F,  GS  and  h  show  the  presence  of  hy- 
drogen ;  whilst  iron,  magnesium,  and  other  elements  have 
also  been  severally  detected  in  turn. 

The  same  principle  has  now  been  applied  to  the  spectra 
of  stars.  In  their  case,  as  in  the  case  of  the  spectrum  of 
the  sun,  the  bright  background  of  the  continuous  spec- 
trum shows  the  presence  of  a  stellar  photosphere,  the  dark 
lines  crossing  it  the  presence  of  particular  gases  in  the 
stellar  atmosphere.  But  the  work  of  identifying  these 
gases  in  connection  with  the  stars  was  one  of  far  greater 
difficulty  than  it  had  been  in  the  case  of  the  sun,  owing  to 
the  light  even  of  the  brightest  stars  being  comparatively  so 
feeble.  This  task  was,  however,  undertaken  by  Huggins 
and  Miller  with  the  utmost  skill  and  patience,  and  hydro- 
gen, sodium,  magnesium,  iron,  calcium  and  other  elements 
which  had  been  previously  detected  in  the  sun  were  shown 
to  exist  in  the  atmospheres  of  Arcturus,  Aldebaran,  and 
several  other  stars. 

For  such  researches  as  those  of  Huggins  and  Miller 


I40  THE  STORY  OF  THE  STARS. 

the  object-glass  prism  of  Fraunhofer  was  quite  unsuited, 
and  a  slit  spectroscope  was  adopted.  In  this  a  very  nar- 
row slit  occupies  the  focus  of  the  telescope,  so  that  the 
image  formed  by  the  telescope  falls  upon  it.  The  slit  is 
also  in  the  focus  of  a  small  object-glass  placed  behind  it, 
called  the  collimator,  which  renders  the  rays  of  light  com- 
ing from  the  star  parallel  to  each  other.  The  rays  then 
pass  through  one  or  more  prisms  and  so  become  dis- 
persed, the  differently  coloured  rays  undergoing  a  different 
amount  of  bending  out  of  their  course.  Finally  the  spec- 
trum thus  produced  is  viewed  by  means  of  a  small  tele- 
scope. As  the  normal  image  of  a  star  is  only  a  point  the 
resulting  spectrum  is  only  a  line,  and  a  small  breadth  has 
to  be  imparted  to  it  by  means  of  a  cylindrical  lens  before 
it  can  be  successfully  observed. 

A  labour  of  a  different  character  was  being  undertaken 
by  Secchi  at  about  the  same  time  that  Huggins  and  Miller 
were  at  work.  This  distinguished  Italian  physicist  found 
that  though  the  spectra  of  different  stars  differed  in  charac- 
ter, these  differences  might  easily  be  reduced  to  no  more 
than  3  or  4  simple  types.  Rutherfurd  had  made  a  similar 
suggestion  a  little  earlier,  but  Secchi  was  the  first  to  carry 
out  a  systematic  spectroscopic  examination  of  any  con- 
siderable number  of  stars.  More  recently,  other  and  more 
detailed  classifications  have  been  proposed  by  Vogel  and 
by  Lockyer  and— as  regards  the  photographs  of  stellar 
spectra — by  Pickering,  but  these  have  in  no  way  super- 
seded Secchi's  scheme  of  classes  ;  they  have  supplemented 
it  rather  than  replaced  it. 

Secchi  divided  the  stars  into  4  principal  groups,  which 
he  designated  "  Types  "  : — (I.)  The  white  or  bluish  stars, 
of  which  Sirius  may  be  taken  as  the  type.  These  stars 
yield  spectra  with  the  lines  of  hydrogen  very  broad  and 
dark,  but  the  lines  of  the  metals  faint  and  difficult  to  see, 
or  altogether  absent.     (II.)  The  yellow   stars,  of  which 


APPLICATION  OF  SPECTROSCOPE  TO  STARS.    1 41 

our  Sun.  Arcturus,  and  Capella  may  be  taken  as  the  chief 
types.  The  spectra  of  these  show  the  lines  of  hydrogen, 
but  not  so  broadly  or  prominently  as  in  the  case  of  the  1st 
type ;  the  metallic  lines  are,  however,  on  the  other  hand, 
numerous  and  distinct.  (III.)  The  orange  stars,  of  which 
a  Orionis,  a  Herculis,  and  the  variable  star  Mira  Ceti  are 
types.  This  class  also  includes  divers  variable  stars  of 
long  or  irregular  period.  The  spectra  are  crossed  by  a 
number  of  dark  bands,  very  dark  and  sharp  on  the  side 
nearest  the  blue,  and  shading  off  gradually  towards  the 
red  end.  (IV.)  The  red  stars,  none  of  which  are  brighter 
than  5th  magnitude.  These  have  spectra  crossed  princi- 
pally by  3  dark  bands,  due  to  the  absorption  of  carbon, 
and  shaded  the  reverse  way  to  those  of  the  Ilird  type. 

A  number  of  small  stars,  distributed  along  the  axis  of 
the  Milky  Way,  and  commonly  called  the  "  Wolf-Rayet  " 
stars,  from  the  two  French  astronomers  who  found  the 
first  examples,  are  now  considered,  in  accordance  with  a 
suggestion  of  Pickering's,  to  form,  together  with  the 
planetary  nebulae,  a  Vth  general  type.  These  show  very 
characteristic  spectra,  the  background  being  of  irregular 
brightness  and  crossed  by  two  bright  lines  in  the  yellow, 
by  another  in  the  light  green,  and  by  a  distinctive  bright 
band  in  the  blue. 

There  are  also  a  few  stars  which  can  scarcely  be 
brought  under  any  of  the  foregoing  five  heads.  For  in- 
stance, many  of  the  stars  in  Orion  have  the  hydrogen  as 
well  as  the  metallic  lines  narrow  and  faint ;  they  can 
therefore  hardly  be  placed  under  either  the  1st  or  Ilnd 
types.  And  it  may  be  added  that  y  Cassiopeiae,  /3  Lyrse, 
and  a  few  other  stars  show  the  hydrogen  lines  bright. 

Secchi's  catalogue  contained  about  500  stellar  spectra, 
but  this  number  has  been  very  largely  increased  by  Vogel, 
who  has  informed  us  concerning  the  spectra  of  about 
4000  stars  ;  whilst    Konkoly  has  dealt  with   about   2000 


142  THE  STORY  OF  THE  STARS. 

.Stars.  All  the  foregoing  were  the  result  of  direct  eye  ob- 
servation, but  a  fuller  survey  has  since  been  accomplished 
by  means  of  photography.  Huggins  at  an  early  period 
applied  photography  to  the  study  of  stellar  spectra,  and 
discovered  thereby  a  remarkable  series  of  broad,  dark 
lines  in  the  ultra-violet  region  of  spectra  of  stars  of  the 
Sirius  type.  Dr.  Henry  Draper  worked  on  similar  lines  at 
about  the  same  time,  and  after  his  death  his  widow  placed 
ample  funds  at  the  disposal  of  the  Harvard  College  ob- 
servatory for  further  researches  to  be  carried  on  in  memory 
of  her  late  husband.  One  of  the  results  of  her  generosity, 
and  of  Pickering's  skilful  use  of  it,  is  the  "  Draper  Cata- 
logue," a  classified  catalogue  of  the  photographed  spectra 
of  more  than  10,000  stars.  The  classification  adopted  is 
somewhat  more  detailed  than  Secchi's,  but  proceeds  on 
essentially  the  same  lines. 

In  a  previous  chapter  (XH.)  I  have  said  a  good  deal 
about  that  remarkable  class  of  objects  commonly  called 
the  temporary  stars,  or  Novce — stars  which  have  suddenly 
come  into  view  and  have  then  rapidly  faded  away.  Only 
a  few  instances  have  occurred  since  the  application  of  the 
spectroscope  to  stellar  observation,  and  the  stars  have  all 
been  much  less  bright. and  enduring  than  Tycho's  famous 
star  of  1 572,  but  striking  characteristics  have  been  exhib- 
ited by  each  of  those  which  have  been  spectroscopically 
treated. 

The  spectrum  of  T  Coronse  in  1866  showed,  besides 
a  continuous  spectrum  crossed  by  dark  lines,  a  number 
of  bright  lines,  amongst  which  those  of  hydrogen  were 
clearly  to  be  noticed.  In  Nova  Cygni  in  1876,  again,  a 
number  of  bright  lines  were  seen  superposed  on  a  con- 
tinuous spectrum.  These  bright  lines  appeared  on  the 
whole  to  correspond  to  those  of  the  solar  chromosphere 
(the  narrow  red  fringe  seen  surrounding  the  sun's  disc 
during  a  total  solar  eclipse).     The  hydrogen  lines,  and  a 


APPLICATION  OF  SPECTROSCOPE  TO  STARS.  143 

characteristic  line  in  the  yellow,  near  the  D  lines  of  so- 
dium, and  called  D3  (or  the  "  Helium  "  line),  were  the 
most  conspicuous.  It  must  be  noted  in  this  connection 
that  the  hydrogen  lines  with  the  D3  line  are  also  the  chief 
lines  exhibited  by  the  "red  flames,"  or  "prominences," 
which  are  often  seen  to  rise  from  the  solar  chromosphere 
to  heights  of  100,000  miles  or  more.  It  follows  from  this, 
therefore,  that  T  Coronse  and  Nova  Cygni  seemed  to  offer 
evidence  that  stars  are  not  only  sometimes  composed  of 
the  same  elements  as  the  sun,  and,  like  it,  possess  pho- 
tospheres surrounded  by  absorbing  gases,  but  also  that 
they  possess  chromospheres  and  prominences,  so  that,  in 
point  of  fact,  the  sudden  development  of  brilliancy  re- 
corded in  the  case  of  these  2  stars  was  really  in  the 
nature  of  a  prodigious  chromospheric  outburst. 

Nova  Cygni,  however,  underwent  further  changes. 
When  its  continuous  spectrum  had  nearly  faded  out  the 
aspect  of  the  spectrum  that  remained  greatly  resembled 
that  of  the  Wolf-Rayet  stars.  Later  still,  in  the  autumn 
of  1877,  the  light  of  the  star  appeared  concentrated  in  a 
single  bright  line,  apparently  the  line  characteristic  of  the 
nebulas. 

Near  the  centre  of  the  great  nebula  in  Andromeda  a 
new  star  became  visible  in  August,  1885.  Its  spectrum 
was  practically  continuous. 

Two  other  N'ovcb  have  yet  to  be  mentioned.  Nova  Au- 
rigas  and  Nova  Normas,  the  last  named  apparently  a  faint 
copy  of  the  first.  Nova  Auriga  stands  out  as  perhaps 
the  most  interesting  and  most  perplexing  object  yet  stud- 
ied by  aid  of  the  spectroscope.  Discovered  by  Dr.  Thomas 
Anderson  on  January  24,  1892,  but  recorded  by  the  auto- 
matic stellar  camera  of  Harvard  College  on  December  10, 
1 891,  it  showed,  when  subjected  to  spectroscopic  analysis, 
the  twofold  spectrum  seen  in  T  Corouce  and  Nova  Cygni, 
a  continuous  spectrum  crossed  by  dark  lines,  and  a  spec* 


144  THE  STORY  OF  THE  STARS. 

trum  of  bright  lines,  amongst  which  those  of  hydrogen 
were  conspicuous,  together  with  many  of  the  principal 
lines  of  the  solar  chromosphere. 

The  star  diminished  in  brightness  very  quickly  after 
March  i6,  1892,  and  was  unfavourably  placed  for  some 
months.  When  it  was  examined  afresh  on  August  17  by 
the  Lick  observers,  it  was  found  to  have  undergone  a  par- 
tial revival,  and,  as  in  the  case  of  Nova  Cygni,  they 
thought  its  spectrum  closely  resembled  that  of  a  planet- 
2X)'  nebula.  Huggins,  however,  did  not  regard  this  con- 
clusion as  fairly  established.  The  spectrum  showed,  it  is 
true,  two  bright  bands  near  the  positions  of  the  two  chief 
nebular  lines,  but  the  bands  were  really  groups  of  bright 
lines,  extending  over  a  considerable  length  of  the  spec- 
trum. The  most  striking  feature  of  the  spectrum  of 
Nova  Aurigae  was  the  displacement  of  its  lines.  As  first 
seen,  the  bright  hydrogen  lines  were  accompanied  by 
dark  absorption  lines,  manifestly  due  to  the  same  element, 
but  displaced  towards  the  violet  as  compared  with  the 
bright  hnes.  Photographs  of  the  spectrum  revealed 
further  details.  Many  of  the  dark  lines  carried  a  fine 
bright  line  upon  them  ;  many  of  the  bright  lines  could  be 
resolved  into  two  or  three  components.  Here,  then, 
there  was  at  least  a  double  hydrogen  spectrum  ;  one  of 
dark  lines,  the  other  of  bright  lines,  the  two  displaced 
with  regard  to  each  other.  Possibly  there  were  several 
such  distinct  spectra.  How  were  their  displacement  with 
regard  to  each  other  to  be  explained  } 

Doppler,  in  1843,  had  shown  that  the  motion  of  a 
source  of  light  towards  the  observer  must  cause  a  short- 
ening of  the  intervals  between  the  waves  of  light.  In 
other  words,  light  of  a  given  special  wave-length  would 
have  that  wave-length  diminished,  and  the  light  would 
appear  to  have  shifted  its  place  in  the  spectrum  towards 
the  blue  end  if  the  source  01  the  light  were  in  motion 


APPLICATION  OF  SPECTROSCOPE  TO  STARS.  145 

towards  us.  If  we  adopt  this  explanation  of  the  com- 
posite spectrum  of  Nova  Aurigas  it  follows  that  that  star 
must  have  consisted  of  two  or  more  bodies  moving  in 
different  directions  in  the  line  of  sight  with  the  most 
amazing  velocity.  The  body  giving  the  dark  absorption 
lines  would  appear  to  have  been  approaching  our  system 
at  a  speed  of  400  or  500  miles  a  second,  and  the  body 
giving  the  bright  lines  to  have  been  receding  at  a  speed 
of  about  300  miles  a  second. 

This  is  scarcely  the  place  to  bring  forward  in  detail 
theories  to  explain  these  complicated  spectra.  The  two 
most  favoured  are  the  "  tidal  theory,"  which  supposes 
that  the  near  approach  of  two  great  stars  to  each  other 
has  given  rise  to  immense  tidal  waves  of  highly  heated 
gas,  and  the  "  cosmical  cloud  theory,"  according  to 
which  these  Novcb  are  due  to  the  rush  of  a  swiftly  moving 
star  through  a  nebula. 

Doppler's  principle  (as  has  already  been  briefly  men- 
tioned in  a  previous  chapter)  had  been  applied  to  a  differ- 
ent problem  by  Huggins  in  1867,  who  carefully  compared 
the  position  of  the  green  line  of  hydrogen  as  given  by  a 
vacuum  tube,  with  that  of  the  same  line  in  the  spectrum 
of  Sirius.  Later  on  he  examined  the  spectra  of  a  number 
of  stars,  and  calculated  from  the  amounts  and  direction  of 
the  displacement  of  the  lines  in  their  spectra,  the  speed  at 
which  the  separate  stars  were  moving  towards  us,  or 
away  from  us  in  the  line  of  sight.  This  research  was 
then  taken  up  at  Greenwich  and  at  Rugby,  but  with  in- 
sufficient means.  Lastly,  Vogel  pressed  photography 
into  the  service,  and  made  some  very  successful  observa- 
tions on  about  50  stars. 

One  result  of  Vogel's  work  was  the  discovery  of  "  spec- 
troscopic double  stars."  The  variable  star,  Algol,  had 
long  been  suspected  to  have  a  dark  companion,  which  by 
transiting  before  its  primary  caused  a  partial  eclipse  every 


146  THE  STORY  OF  THE  STARS. 

69  hours.  Vogel  now  conclusively  showed  that  this  was 
the  case,  for  Algol  was  moving  round  the  centre  of  gravity 
of  the  pair  in  precisely  the  time  required,  and  the  diame- 
ter, mass,  distance  from  its  primary,  and  speed  in  its  orbit, 
of  the  unseen  companion,  were  all  computed. 

Spica  Virginis  proved  to  be  another  close  double, 
though  in  this  case  the  companion  does  not  obscure  the 
bright  principal  star.  Indeed,  it  is  possible  that  it  is  as 
bright  as  the  3rd  magnitude. 

In  some  cases  a  "  spectroscopic  double  "  is  composed 
of  two  stars  of  nearly  equal  brightness.  This  is  the  case 
with  ^  Ursae  Majoris  and  /3  Aurigce,  which  were  discovered 
by  Pickering  a  little  before  Vogel's  proof  of  the  existence 
of  the  companion  of  Algol.  The  two  stars  which  make 
up  ^  Aurigas  revolve  in  an  orbit  which  is  but  little  inclined 
to  the  line  of  sight.  Consequently  at  one  time  one  star 
will  be  approaching  us  in  its  orbit  whilst  the  other  is  re- 
ceding. The  lines  due  to  the  first  star  are  displaced 
towards  the  blue,  and  those  of  the  second  towards  the 
red,  and  the  lines  in  the  compound  spectrum  are  therefore 
double.  A  little  later  both  bodies  are  moving  across  the 
line  of  sight,  and  therefore  are  neither  approaching  us  nor 
receding  from  us,  so  that  the  lines  of  the  two  stars  exactly 
coincide.  The  period  in  the  case  of  this  star  is  nearly  4 
days. 

Another  probable  "  spectroscopic  double  "  is  the  vari- 
able star  /3  Lyrte.  This  star  (as  we  have  already  seen) 
goes  through  its  changes  in  a  little  less  than  13  days,  hav- 
ing two  maxima  and  two  minima.  Its  spectrum  shows 
broad,  dark  bands,  due  to  hydrogen,  besides  bright  lines, 
which  change  their  appearance  and  position  from  time  to 
time.  It  has  been  suggested  that  the  system  consists  of 
two  stars  of  unlike  spectra  revolving  round  each  other, 
and  partially  eclipsing  each  other  as  they  cross  the  line  of 
sight.     The  changes  of  the  spectrum  are,  however,  very 


APPLICATION  OF  SPECTROSCOPE  TO  STARS.  1 47 

complicated,  and  have  not  yet  been  completely  studied, 
and  so  simple  an  explanation  appears  scarcely  adequate. 

A  very  promising  and  important  study  is  that  of  the 
distribution  of  the  different  types  of  stellar  spectra.  For 
this  the  available  material  is  as  yet  insufficient.  Never- 
theless, the  Draper  catalogue,  and  the  catalogues  of  Vogel 
and  Konkoly,  have  enabled  some  first  approximations  to 
be  made.  It  appears,  from  a  consideration  of  such  binary 
stars  as  have  been  spectroscopically  examined,  that  the 
1st  or  Sirius  type  of  stars  are  much  less  dense  relatively 
to  their  brightness  than  the  Solar  stars,  or  are  intrinsically 
brighter  relatively  to  their  density.  The  Ilnd  type  of 
stars,  /.  e.,  the  Solar  stars,  and  to  a  less  degree  the  Ilird 
type  of  stars,  appear  to  be  pretty  evenly  distributed  over 
the  sky.  The  1st,  or  Sirius  type,  shows  a  distinct  disposi- 
tion to  aggregation  towards  the  Milky  Way,  whilst,  as 
already  pointed  out,  the  Wolf-Rayet  stars  cluster  along  its 
axis.  The  proper  motions  of  the  Sirius  stars  appear  to  be 
smaller  than  those  of  the  Solar  stars,  which  from  this 
and  other  reasons  may  be  supposed  to  be  on  the  average 
nearer  to  us  than  the  Sirius  stars.  If  the  Solar  type  stars 
be  divided  into  two  classes,  according  to  their  greater 
resemblance  to  Capella  and  Arcturus  respectively,  the  for- 
mer class  appears  to  have  a  larger  average  proper  motion 
than  the  latter,  and  may  therefore  be  supposed  to  be  the 
nearer  stars.  The  entire  subject,  however,  needs  much 
fuller  investigation  before  any  great  weight  can  be  at- 
tached to  these  provisional  conclusions.  The  completion 
of  the  Draper  catalogue  by  the  publication  of  the  results 
of  the  survey  of  the  southern  heavens  carried  out  at  Are- 
quipa,  in  Peru,  under  the  direction  of  the  Harvard  astrono- 
mers, will  constitute  the  next  important  forward  step. 

The  first  observation  of  the  spectrum  of  a  nebula  was 
made  by  Huggins  in  August,  1864.  The  object  examined 
was  the  small,  bright,  planetary  nebula  in  the  pole  of  the 


148  THE  STORY  OF  THE  STARS. 

ecliptic,  37  ip  IV  Draconis,  to  which  some  allusion  has 
already  been  made.  The  first  scrutiny  revealed  the  fact 
that  there  existed  an  immense  difference  between  its 
spectrum  and  an  ordinary  stellar  spectrum.  In  place  of 
the  usual  continuous  spectrum  only  three  isolated  bright 
lines  were  seen — a  proof  of  the  presence  of  luminous  gas. 
In  other  words,  the  object  was  a  true  nebula,  that  is,  a 
mass  of  glowing  gas,  and  not  a  star  cluster,  seeming  to  be 
nebulous  only  on  account  of  its  distance. 

Of  the  three  lines,  one,  the  faintest,  was  evidently  due 
to  hydrogen.  The  other  two  have  not  yet  been  identified, 
but  the  brightest  is  very  near  one  of  a  pair  of  green  lines 
in  the  spectrum  of  nitrogen,  and  has  hence  been  sometimes 
spoken  of  as  the  "nitrogen  Hne."  Other  lines  due  to 
hydrogen  have  since  been  observed  in  various  nebular 
spectra,  together  with  the  well-known  chromospheric  line 
D3,  A  number  of  other  Hnes  have  also  been  detected  in 
the  visual  spectrum  with  extreme  difficulty  by  different 
observers,  and  many  more  by  means  of  photography  in 
the  violet  and  ultra-violet  regions.  The  sources  of  these 
lines  have  not  yet  been  ascertained,  and  in  a  great  number 
of  the  fainter  spectra  the  line  in  the  green  near  the  nitrogen 
pair,  which  is  especially  to  be  regarded  as  the  typical 
nebular  line,  is  alone  visible. 

The  problem  of  the  motions  of  the  nebulas  in  the  line 
of  sight  has  been  attacked  by  Keeler  at  the  Lick  Observa- 
tory. He  has  measured  the  displacement  of  the  chief 
nebular  line  in  the  spectra  of  the  nebulas,  and  has  obtained 
evidence  of  movements  varying  from  a  speed  of  about  40 
miles  per  second  of  approach,  to  about  30  miles  per 
second  of  recession. 

Several  of  the  nebulas,  as,  for  example,  the  great  nebula 
in  Andromeda,  show  continuous  spectra.  But  many  of 
those  that  give  a  spectrum  of  bright  lines  give  also  a  faint, 
continuous  spectrum.     The  great  nebula  of  Orion  is  one 


APPLICATION  OF  SPECTROSCOPE  TO  STARS.  149 

of  the  latter  class,  though  Huggins  considers  that  the 
seemingly  continuous  spectrum  is  resolvable  into  lines. 
Other  nebulce  show  bright  lines  only,  without  any  trace  of 
continuous  spectrum. 

In  the  case  of  the  great  nebula  in  Orion  Huggins  has 
secured  some  photographs  of  exceptional  interest,  which 
show  that  the  stars  of  the  "  trapezium  "  are  not  merely 
apparently  in  the  nebulas,  but  really  so,  for  a  number  of 
bright  lines  (one  in  particular,  with  a  wave-length  of  3730 
"tenth  metres")  were  observed  both  in  the  continuous 
spectrum  of  two  of  the  trapezium  stars,  and  in  the  spec- 
trum of  the  nebulas  in  their  immediate  neighbourhood.  A 
later  photograph,  taken  in  1889,  in  which  the  slit  of  the 
spectroscope  was  pointed  near  to  the  trapezium,  but  not 
actually  across  it,  failed  to  shew  the  3730  line,  which 
would  thus  appear  to  be  typical  only  of  the  regions  of  the 
nebulae  close  to  the  stars.  It  would  seem  probable,  there- 
fore, that  these  stars  are  involved  in  the  nebulas. 

The  subject  of  spectroscopic  observations  of  the  stars 
and  nebulae  is  a  growing  one,  but  we  have  yet  much 
more  to  do  before  we  can  much  more  learn. 


APPENDIX   I. 


TABLE  OF  THE  CONSTELLATIONS. 


By  the  entries  in  the  column  headed  "  Centre  "  it  is 
meant  to  be  inferred  that  a  line  of  Right  Ascension  and  a 
line  of  Declination  taken  off  the  map  will  intercept  at  a 
point  which  may  be  regarded  as  about  the  centre  of  the 
constellation.  This,  however,  is  only  true  of  the  more 
compact  constellations,  for  there  are  some,  like  Draco, 
Cetus,  and  Argo,  which  are  so  long  and  straggling  that 
they  extend  over  several  hours  of  RA.  When,  therefore, 
I  state  that  the  constellations  are  here  arranged  in  the 
order  of  R.A.,  the  statement  must  be  regarded  as  need- 
ing some  qualification  in  many  cases.  In  the  column  of 
"  Declination  "  -f-  means  North,  and  —  South. 


Name  of  Constellation. 


Pisces 

Sculptor  [Apparatus  Sculptoris] , 

Andromeda 

Phoenix 

Cassiopeia 

Cetus.. 

Triangulum 

Fornax  [Chemica] 

Aries 

Hydrus 

Perseus 

ISO 


CENTRE. 

R.A. 

Decl. 

h.  m. 

0 

o  20 

+  10 

0  30 

-35 

0  40 

+  38 

I   0 

-48 

I   0 

+  60 

I  45 

—  12 

2  0 

+  32 

2  25 

—33 

2  30 

+  20 

2  40 

-72 

3  20 

+,42 

THE  CONSTELLATIONS. 


151 


Name  of  Constellation. 


Horologium 

Reticulum  [Rhomboidalis] 

Eridanus 

Taurus 

Caelum  [Caela  Sculptoris].. 

Dorado 

Orion 

Lepus 

Pictor  [Equleus  Pictoris].. 
Mensa  [Mons  Mensa]  . . . . 

Columba  [Noachi] 

Camelopardus 

Auriga 

Canis  Major 

Gemini 

Monoceros 

Canis  Minor 

Argo  [Puppis] 

Lynx 

Argo 

Cancer 

Argo  [Carina] 

Volans  [Piscis  Volans].. . . 

Argo  [Malus] 

Argo  [Vela] 

Antlia  Pneumatica 

Sextans 

Leo  Minor 

Leo 

Chamaeleon 

Hydra 

Ursa  Major 

Crater 

Crux 

Corvus 

Musca  Australis 

Coma  Berenices. . , 

Canes  Venatici 

Centaurus 


CENTRE. 

R.A. 

Decl. 

h.  m. 

0 

3  20 

-52 

3  50 

-63 

3  50 

-30 

4  30 

+  18 

4  40 

-42 

5  0 

-60 

5  20 

+  3 

5  25 

—  20 

5  30 

-52 

5  40 

-77 

5  40 

-34 

5  40 

+  70 

6  0 

+  42 

6  40 

-24 

7  0 

+  24 

7  0 

-  3 

7  30 

+  6 

7  40 

-32 

7  50 

+  45 

8  0 

-40 

8  30 

+  20 

8  40 

-62 

8  40 

-69 

9  0 

-30 

9  30 

-45 

10  0 

-35 

10  10 

—  I 

10  20 

+  33 

10  30 

+  15 

10  40 

-78 

II  0 

—  12 

II  0 

+  58 

II  20 

-15 

12  20 

-60 

12  30 

-18 

12  30 

-68 

12  40 

-27 

13  0 

4-40 

13  20 

-47 

152 


APPENDIX  I. 


Name  of  Constellation. 


Virgo 

Booces 

Circinus 

Lupus 

Libra 

Apus 

Serpens 

Corona  Borealis 

Triangulum  Australe.  . 

Ursa  Minor 

Norma 

Draco 

Scorpio 

Ara 

Ophiuchus .* .  . 

Hercules 

Corona  Australis 

Scutum  Sobieskii 

Telescopium 

Lyra 

Sagittarius 

Pavo 

Aquila  (with  Antinoiis) 

Sagitta 

Vulpecula  et  Anser.. . . 

Cygnus 

Delphinus 

Capricornus 

Microscopium 

Equuleus 

Indus 

Piscis  Australis 

Cepheus 

Grus 

Aquarius 

Lacerta 

Pegasus 

Toucan 

Octans 


R.A. 

Decl. 

h.  m. 

0 

13  20 

—  2 

14  35 

+  30 

14  50 

-63 

15   0 

—40 

15  10 

-14 

15  30 

-76 

15  35 

+  8 

15  40 

4-30 

15  40 

-65 

15  40 

+  78 

16  0 

-49 

16  0 

+  60 

16  20 

-26 

16  50 

-55 

17  10 

—  4 

17  10 

+  27 

18  30 

—41 

18  30 

—  10 

18  40 

-52 

18  45  ■ 

+  36 

19  0 

-25 

19  10 

-65 

19  30 

+  2 

19  50 

4-18 

20  10 

+  25 

20  30 

+  40 

20  35 

+  12 

20  50 

—  20 

21  0 

-37 

21  10 

+  6 

21  20 

-58 

21  40 

-32 

22  0 

4-70 

22  20 

-47 

22  20 

-13 

22  25 

+  43 

22  30 

+  17 

23  45 

-68 

Polar 

(South) 

APPENDIX   II. 

LIST     OF     CELESTIAL     OBJECTS      FOR     SMALL     TELE- 
SCOPES.* 

It  is  here  assumed  that  a  certain  number  of  the  read- 
ers of  this  volume  may  happen  to  possess  a  small  tele- 
scope, and  would  be  glad  to  direct  it  on  celestial  objects 
of  interest  if  they  knew  where  to  look  for  some  which 
were  within  the  reach  of  their  instruments.  Hence  the 
motive  for  the  compilation  of  this  catalogue,  which  may 
be  said  to  represent  the  capacity  of  portable  refracting 
telescopes  of  about  2  inches  in  aperture. 

(l)   DOUBLE  OR  COMPOUND   STARS. 


No. 

Name  of  Star. 

Right 
Ascen- 
sion, 1890. 

Declina- 
tion, 
1890. 

Magnitudes 
of  Com- 
ponents. 

Distance 
between  the 
Components. 

t 
2 

3 

)3  Toucani 
T]  Cassiopeise 
7  Arietis 

h.    m.    s. 
0  26  30 

0  42   26 

1  47  29 

0      / 

-63  34 
+  57  13 
+  18  45 

Both  5 
4  and  7^ 
4i  and  5 

n 

28 

5 
8 

4 

7  Andromedse 

I  57     8 

+  41  48 

3|  and  si 

5    10:  B. 

\    double. 
8 

14 
31 

53 

5 
6 

7 
8 

d  Eridani 
14  Aurigae 
23  Orionis 
S  Orionis 

2  54     5 
5     8  14 
5  17     3 
5  26  23 

—40  44 
-r32  33 
+   3  26 
—  0  22 

5  and  6 
5  and  7i 
5  and  7 
2  and  7 

*  T^or  a  comprehensive  general  catalogue  of  objects  of  this  kind, 
with  full  descriptions  of  each,  see  Admiral  W.  H.  Smyth's  "  Cycle 
of  Celestial  Objects,"  2nd  ed.,  Oxford,  1881,  price  12s. 
153 


154 


APPENDIX  II. 


Right 

Declina- 

Magnitudes 

Distance 

No. 

Name  of  Star. 

Ascen- 

tion, 

of  Com- 

between the 

sion,  1890. 

1890. 

ponents. 

Components. 

9 

<r  Orionis 

h.    m.    s. 

5  33    3 

0      / 

-   238 

4,  8  and  7 

// 
j  12  and  42  : 
/    multiple. 

10 

II  Monocerotis 

6  23  29 

-  6  57 

6i,  7  and  8 

j        7,9: 
I  (B.C.=2.5) 

II 

7  Volantis 

7    9  40 

-70  19 

5  and  7 

13 

12 

a  Geminorum 

7  27  35 

+  32    7 

3  and  3i 

5 

13 

7  Argus 

8     6     8 

—47    0 

2  and  6 

42 

14 

54  Leonis 

10  49  39 

-4-25  20 

4i  and  7 

6 

15 

0  Crucis 

12  20  28 

—62  29 

i-J,  2  and  5 

j      5,90: 
I   qumtuple 
j     145  [use 
(  low  power] 

l6 

17  Comae  Ber. 

12  23  25 

+  26  30 

4-J  and  6 

17 

7  Crucis 

12  25     2 

-56  29 

2  and  5 

120 

i8 

7  Virgin  is 

12  36     5 

—  0  50 

both  4 

5 

19 

a  Can.  Venat. 

12  50  53 

+  38  54 

2i  and  6i 

20 
(  14 ;  Alcor, 

20 

CUrs^Maj. 

13  19  29 

+  55  30 

3  and  5 

<  mag.  5,  is 
(  distant  ilf 

21 

a  Centauri 

14  32    7 

—60  22 

I  and  2 

14 

22 

IT  Bootes 

14  35  33 

+  16  53 

3^  and  6 

J'    1 

23 

1  Scorpii 

15  58  19 

—II     4 

4i  and  7i 

j  7  ;  A.  also 
(     double 

24 

j8  Scorpii 

15  59    2 

-19  30 

2  and  5i 

j  13;  A.  also 
}      double 
(   40 ;  both 

25 

V  Scorpii 

t6    5  36 

— ig  10 

4  and  7 

■j     double 

(       0.7,  2 
4 

26 

36  (A)  Ophiuchi 

17     8  34 

—26  25 

4i  and  6i 

27 

0  Herculis 

17    9  38 

+  14  30 

3i  and  si 

4 

28 

CLyrse 

18  40  59 

+  37  29 

5  and  5i 

44 

29 

d  Serpentis 

18  50  49 

+  43 

4i  and  5 

21 

30 

)8  Cygni 

19  26  17 

+  27  43 

3  and  7 

34 
(    376  [use 
(  low  power] 

31 

o'^  Capricomi 

20  II  57 

-12  53 

3  and  4 

32 

$^  Capricomi 

25  14  50 

-15     7 

3i  and  7 

205 

33 

7  Delphini 

20  41  33 

+  15  43 

4  and  6-^ 

II 

34 

)8  Cephei 

21  27  14 

+  70    4 

3  and  8 

13 

35 

5  Cephei 

22  25     5 

+  57  51 

4i  and  7 

40 :  A.  van 

LIST  OF  CELESTIAL  OBJECTS. 


155 


(2)  CLUSTERS  OF  STARS  AND  NEBULAE. 


No. 

Designation  of  Object. 

Nature  of 
Object. 

Right  As- 
cension. 

DeclinaP 
tion. 

h. 

m.     s. 

0      / 

I 

47  Toucani 

Cluster 

0 

19      9 

-72  41 

2 

31  M.  Andromedae 

Nebula 

0 

36  47 

+  40  40 

3 

The  Nubecula  Minor 

0 

48  41 

-73  58 

4 

103  M.  Cassiopeise 

Field  of  stars 

I 

25  56 

+  60     7 

5 

33  I^l  VI  Persei 

Double  cluster 

2 

II  20 

+  56  38 

6 

7}  Tauri 

Group  of  stars 

3  40  56 

+  23  45 

7 

Nubecula  Major 

5 

24     6 

-69  34 

8 

I  M.  Tauri  ["Crab"] 

Nebula 

5 

27  51 

+  21  56 

9 

42  M.  Orionis 

Nebula 

5 

29  52 

-  5  27 

10 

35  M.  Geminorum 

Cluster 

6 

2     4 

+  24  26 

II 

41  M.  Canis  Majoris 

Cluster 

6 

42  13 

-20  37 

12 

"  Praesepe  "  in  Cancer 

Cluster 

8 

33  55 

+  20  19 

13 

rj  Argus 

Nebula 

10 

40  47 

-59    6 

14 

K  Crucis 

Cluster 

12 

47     7 

-59  45 

15 

a>  Centauri 

Cluster 

13 

20  10 

-46  44 

16 

3  M.CanumVenaticorum 

Cluster 

13 

37     3 

+  28  55 

17 

5  M.  Librae 

Cluster 

15 

12  57 

+  2  30 

18 

So  M.  Scorpii 

Cluster 

16 

10  26 

-22  43 

19 

13  M.  Herculis 

Cluster 

16 

37  45 

+  36  39 

20 

92  M.  Herculis 

Cluster 

17 

13  46 

+  43  15 

21 

14  M.  Ophiuchi 

Cluster 

17 

31  50 

-  3  II 

22 

8  M.  Sagittarii 

Cluster 

17 

57     8 

—  24  22 

23 

24  M.  Scuti  Sobieskii 

Cluster 

18 

II  44 

-18  26 

24 

17  M.  Scuti  Sobieskii 
["  Horse-shoe  "j 

Nebula 

18 

14  16 

—  16  14 

25 

22  M.  Sagittarii 

Cluster 

18 

29  28 

-23  59 

26 

II  M.  Antinoi 

Cluster 

18 

45  13 

—  6  24 

27 

57  M.  Lyrse 

Annular  neb. 

18 

49  28 

+  32  53 

28 

27  M.  Vulpecula 
["Dumb-bell"] 

Nebula 

19 

54  48 

+  22  25 

29 

15  M.  Pegasi 

Cluster 

21 

24  38 

+  11  40 

30 

2  M.  Aquarii 

Cluster 

21 

27  44 

-  I  19 

156 


APPENDIX  II. 


(3)  SPECIAL  STARS. 


Right 

Declina- 

No. 

Name  of  Stars. 

Ascension, 
1890. 

tion, 

1890. 

Mag. 

Notes. 

h.    m.     s. 

0      / 

I 

oCeti 

2  13  47 

—  3  28 

Var. 

Max.  mag.  2 : 
Fiery  red.  In- 
visible at  Min. 

2 

aCeti 

2    56   31 

+   3  39 

2i 

Orange  colour 

3 

P  Persei 

3      I      2 

+  40  31 

Var. 

Max.  2  :  Min.  4 

4 

5  Lyncis 

6  17  12 

+   8  28 

5i 

Fiery  red 

5 

/i  Canis  Majoris 

6  51     3 

-13  54 

5i 

Fiery  red 

6 

20918  Lai.  Hydrae 

10  46  16 

-20  37 

7 

Copper  coloured 

7 

)8  Libra 

15  II     5 

-  8  58 

2i 

Pale  green 

8 

a  Scorpii 

16  22  39 

—  26  II 

I 

Fiery  red 

9 

X  Cygni 

19  46  20 

+  32  38 

Var. 

Max.  4:  Min.  in- 
visible 

10 

/t  Cephei 

21  40     8 

+  58  16 

Var. 

Max.  4  :  Min.  6  : 
Deep  garnet 
colour 

II 

S  Cephei 

22  25     5 

+  57  51 

Var. 

Max.  3|-:  Min.  4^ 

12 

8  Andromedse 

23  12  38 

+  48  24 

5 

Fiery  red 

13 

30  Piscium 

23  56  19 

-  6  37 

4i 

Fiery  red 

GENERAL   INDEX. 


Achernar  (a  Eridani),  24. 

Airy,  Miss,  103. 

Alcyone,  one  of  the  Pleiades,  103. 

Aldebaran  (a  Tauri),  23,  24,  32,  33, 

34,  35,  70. 
Algol  (P  Persei),  32,  33,  86,  145. 
Almanacks,  based  on  astronomy,  10. 
Altair  (a  Aquilae),  24,  25. 
Amos,  Prophecy  of,  cited,  40,  102. 
Andromeda   (constellation),    32,   34, 

Great  Nebula  in,  jq,  116,  148. 

Angle  of  position  of  double  star,  54, 

Annular  Nebulae j  115. 

Antares  (a  Scorpii),  23,  24,  25,  34. 

Antinoiis,  152. 

Antlia  Pneumatica    (constellation). 

Apparatus  Sculptoris  (constellation), 

150. 
Apparent  movement  of  the  heavens, 

II. 
Apus  (constellation),  152. 
Aquarius  (constellation),  35. 
Aquila  (constellation"),  34. 
Ara  (constellation),  152. 
Arago,  92. 
Aratus,  42. 
Arcturus  (a  Bootes),  23,  24,  34,  70, 

71,  141. 
Argelander,  F.  G.  A.,  43,  85. 
Argo  (constellation),  151.     • 

Great  Nebula  in,  124,  129. 

Tj,  Variable  in,  88. 

Aries  (constellation),  33,  35,  39. 
— ;-  First  point  of,  37. 
Aristotle,  135. 
Ascension,  Right,  37. 
Atlases,  Celestial,  39. 
Auriga  (constellation),  151. 
Auwers,  A,  103. 


Axis  of  the  heavens,  15. 
Azimuth,  18. 

B. 

Bayer,  J.,  his  Atlas,  85. 

his  lettering  of  the  stars,  23. 

Bessel,  F.  W.,  58. 

Betelgeuse  (a  Orionis),  24. 

Bible,  References  to,  40,  102. 

Binary  stars,  55. 

Biot,_E.,  77. 

Birmingham,  J.,  78. 

Bond,  G.  P.,  117. 

Bootes  (constellation),  152, 

Bradley,  J.,  71. 

Brisbane,  Sir  T.  M.,  88. 

Burchell,  his  observations  of  r}  Ar« 

gus,  88. 
Byron,  Lord,  Quotation  from,  99. 

C. 

Caela  Sculptoris  (constellation),  151, 
Camelopardus  (constellation),  151. 
Cancer  (constellation),  35. 
Canes  Venatici  (constellation),  151. 
Canis  Major  (constellation),  33. 
Canis  Minor  (constellation),  33. 
Canopus  (a  Argus),  24. 
Capella  (a  Aurigae),  24,  25,  32,  167. 
Capricornus  (constellation),  34. 
Cassiopeia  (constellation),  31,  32. 
Castor  (a  Geminorum),  34,  35. 
Centaurus  (constellation),  151. 
Central   sun    hypothesis,    Madler's, 

74- 
Cepheus  (constellation),  31,  32. 
Cetus  (constellation),_34,  35. 

J!/ra,  Variable  in,  84,  141c 

Chacornac,  116. 
Chaldean  astronomy,  41, 
Chamaeleon,  151. 
Chandler,  86,  92. 


158 


GENERAL  INDEX. 


Chinese  observations  referred  to,  41, 

76. 
Circinus  (constellation),  152. 
Clusters  of  stars,  loi. 

List  of,  for  small  telescopes,  155. 

Coal  Sack.  The,  131. 
Coloured  stars,  62. 
Columba  Noachi  (constellation),  33. 
Coma  Berenices  (constellation),  106. 
Compass,  Points  of,  17-20. 
Complementary  colours,  65. 
Constellations,  28. 
Constellations,  List  of,  150. 

Brief  account  of,  30. 

Corona  Australis  (constellation),  152. 
Corona  Borealis  (constellation),  34. 
Corvus  (constellation),  151. 
Crab  Nebula  in  Taurus,  122. 
Crater  (constellation),  151. 
Crux  (constellation),  151. 
Cygnus  (constellation),  32. 


Declination,  36. 

Delphinus  (constellation),  34. 

Deneb  (a  Cygni),  24. 

Diodorus,  135. 

Diurnal  Movement,  13. 

Doppler,  72,  144. 

Dorado  (constellation),  151. 

Nebula  in,  123. 

Double  stars,  51,  65. 
Draco  (constellation),  32,  42. 
Draper,  Dr.,  142. 
''Dumb-bell"  Nebula,  127. 

E. 

Egyptian  Astronomy,  40. 
Elliptic  Nebula;,  115,  116. 
Eridanus  (constellation),  151, 
Espin,  T.  E.,  93. 

F. 

"  Fixed"  stars,  12. 

Fomalhaut  (a  Piscis  Australis),  23, 

^24,  25.  34. 

Fontenelle,  69. 

Fornax  Chemica  (constellation),  150. 

Fraunhofer,  137. 

G. 

Galaxy,  49  (see  Milky  Way). 
Gauging  the  heavens,  47. 
Gemini  (constellation),  33,  35. 
Genesis  xv,  5  cited,  43. 
Globular  clusters,  107. 


Goodricke,  86,  87. 

Gore,  J.  E.,  81,  95,  135. 

Gould,  B.  A.,  134. 

Grant,  R.,  44. 

Gravitation    as    applied    to   binary 

stars,  56. 
Greenwich  Observatory,  10. 
Grus  (constellation),  152. 
Greek  alphabet,  23,  30. 

H. 

Halley,  E.,  70,  88. 
Hercules  (constellation),  34. 

cluster  13  M.  in,  106,  155. 

cluster  92  M,  in,  155. 

Herschel,  Sir  W.,  46,  53,  55,  73,  74, 

107,  108,  113,  119,  134. 
Herschel,  Sir  J.  F.  W.,  46,  63,  67,  88, 

106,     III,    114,    117,     121,     122,     123, 
124,   125. 

Herschel,  Capt.  J.,  125. 

Hesiod,  42. 

Hind,  J.  R.,  78,  92,  104,  121. 

Hipparchus,  77. 

Holden,  E.,  120. 

Huggins,   W.,  73,    74,  92,  116,  13s, 

139,  140,  i44j  147. 
Hyades,  The,  in  Taurus,  33, 102, 105. 
Hydrus  (constellation),  150. 


Indus  (constellation),  152. 

J. 

Jacob's    Ladder,   name    for   Milky 

Way,  136.  ^ 
Job  ix,   9    cited,  40,   102 ;    xxxviii, 

31-2,  40,  102. 

K. 
Key,  Rev.  H.  C,  121. 
Kirchhoff,  138. 
Klein,  H.  J.,  his  Atlas  referred  to, 

39- 
Konkoly,  141. 


LaCaille,  N.  L.,  88,  108. 
Lacerta  (constellation),  152. 
Leo  (constellation),  33,  35. 
Leo  Minor  (constellation),  151. 
Lepus  (constellation),  151. 
Libra  (constellation),  35. 
Lockyer,  J.  N.,  140. 
Longfellow,  Quotation  from,  100. 
Lupus  (constellation),  152. 


GENERAL  INDEX. 


159 


Lynx  (constellation),  151. 
Lyra  (constellation),  152. 

quadruple  star,  e,  60. 

• Annular  Nebula  in,  115. 

M. 

Madler,  J.  H.,  74. 
Magellanic  Clouds,  127. 
Magnitudes  of  stars,  21. 

,  List  of  stars  of  the  first,  24. 

Maia  (one  of  the  Pleiades),  103. 
Manilius,    his    description     of     the 

Milky  Way,  136. 
Mazzaroth,  Meaning  of,  41. 
Mechain,  108. 

Meridian,  17,  37.  ,        ,    , 

Messier,  his   catalogue   of   nebulae, 

108,  122. 

No.  I,  122,  155. 

No.  5,  108. 

No.  II,  113,  155. 

No.  13,  106. 

Metrodorus,  his  idea  of  the  Milky 

Way,  135. 
Micrometer,  54. 

Microscopium  (constellation),  152. 
Milky  Way.  its  course  amongst-  the 

stars,  80,  129. 

Theories  of,  134. 

Various  old  names  of,  136. 

Miller,  W.  A.,  130,  140. 
Milton,  J.,  Quotations  from,  97. 
Mira  (o)  Ceti,  84,  i56._ 
Monoceros  (constellation),  151. 
Mons  Mensae  (constellation),  151. 
Montanari,  86. 

Moore,  T.,  Quotations  from,  99. 
Motions  of  the  stars,  apparent,  11. 

in  the  line  of  sight,  146. 

Multiple  stars,  62. 

Musca  Australis  (constellation),  151. 

N. 
Naked  eye,  Number  of  stars  visible 

to,  12,  43,  45. 
Nautical  A  Imajiac  referred  to,  10. 
Nebulae,  114. 
Spectroscopic    observations  of, 

129,  147. 

,  alleged  to  be  variable,  129. 

for  small  telescopes,  155. 

Nebulous  stars,  121. 

New  stars,  142. 

Norma  (constellation),  152. 

Nubecula  Major,  127. 

Nubecula  Minor,  127. 

Number  of  the  stars  visible  to  the 

naked  eye,  12,  43. 


Octans  (constellation),  152. 
"Omega"  Nebula,  126,  129. 
Ophiuchus  (constellation),  34. 

Hind's  Nova  in,  78. 

"Orbis  Lacteus,"  136. 
Orbits  of  double  stars,  56. 
Orion  (constellation),  33. 

Great  Nebula  in,  122,  129,  149. 

Ovid,  Quotations  from,  103,  136. 


Palitzch,  observes  Algol,  86. 
Parallax,  Stellar,  26,  27,  55. 
Pavo  (constellation),  152. 
Pegasus  (constellation),  32,  34,  35. 
Perpetual  apparition.  Circle  of,  14. 
Perpetual  occultation,  Circle  of,  14. 
Perseus  (constellation),  150. 

Cluster  in,  lor. 

Phoenix  (constellation),  150. 
Photography  as  applied  to  stars,  49. 
Pickering,  E.  C,  22,  82,  86,  140. 
Pictor  (constellation),  151. 
Pigott,  his  theory  of  variable  stars, 

91. 
Pingre,  A.  G.,  77. 
Pisces  (constellation),  35. 

Australis  (constellation),  152. 

Volans  (constellation),  151. 

Planetary  nebulae,  118. 
Pleiades,  32  34,  35,  102. 
referred  to  in  Job  and  Amos, 

102. 
possibly  the  centre  of  the  Solar 

System,  75. 

mentioned  by  Homer,  102. 

nebulae  in,  103. 

Pogson,   N.,  Account  of  nebula  in 

Scorpio,  109. 
Pole-star,  Polaris  (a  Ursae  Minoris) 

12,  31,  33,  34- 
Pole,  North,  13. 

,  South,  13. 

Pollux  (|8  Geminorum),  24,  34. 
Position,  Angle  of,  54. 
Praesepe  in  Cancer,  102,  105. 
Precession  of  the  Equinoxes,  37. 
Pritchard,  Rev.  C,  22. 
Proctor,  R.  A.,  134. 
Procyon  (a  Canis  Minoris),  24,  33, 57. 
Proper  motions  of  stars,  67. 
Pythagoras,   his  speculations  as  to 

the  Milky  Way,  136. 


Q. 

Quadruple  stars,  60. 


i6o 


GENERAL  INDEX 


Red  stars,  6-3,,  66,  141. 

Regulus  (a  Leonis),  24,  25,  33,  34,  35- 

Rigel  (/3  Ononis),  24. 

Right  Ascension,  36. 

Roberts,  I.,  his  photographs,  117, 127. 

Rosse,  Earl  of,  various  observations 

by,  106,  115,  117,  118,  119,  121. 
Russell,  H.  C,  his  account  of  k  Cru- 

cis,  114. 

Sagitta  (constellation),  152. 
Sagittarius  (constellation),  35. 

nebulae  in,  125. 

Schiaparelli,  104. 
Schmidt,  J.  F.  J.,  78. 
Schonfeld,  E.,  no. 
Scorpio  (constellation),  35. 

cluster  80  M,  108. 

Sculptor  alias  Apparatus  Sculptoris 

(constellation),  150. 
Scutum  Sobieskii  (constellation),  152. 

Nebula  in,  126. 

Secchi,  A.,  45,  116,  123,  140. 

his  classification  of  star  spectra, 

140. 
Seidel,  22,  44. 

Serpens  (constellation),  152. 
Sextant  (constellation),  33. 
Shakespeare,  W.,  Quotations  from, 

95- 
Shelley,  Quotations  from,  99. 
Signs  of  the  Zodiac,  38  {see  Zodiac). 
Sirius  (a  Canis  Majoris),  24,  25,  27, 

57,  70,  91,  140. 
Smyth,  Admiral  W.  H.,  106, 108, 112, 

Spectroscopic   observation   of  stars, 
137. 

of  nebulae,  147. 

Spica  (a  Virginis),  24,  25,  34,  35. 
Spiral  Nebulae,  115,  "T- 
Stars,  Double,  51,  52,  64. 

Binary,  55. 

Triple,  56,  59. 

Multiple,  62. 

Coloured,  62. 

Variable,  83. 

Temporary,  75,  109,  142. 

Brilliancy  of,  21. 

Motions  of,  67. 

Names  given  to,  23. 

Struve,  F.  G.  W.,  48. 
—  L.,„.  ^ 

Taurus  (constellation),  33,  34.  35' 
"  Crab"  Nebula  in,  122. 


Telescopes,  List  of  objects  for,  153. 

Telescopium  (constellation),  152. 

Tempel,  W.,  103. 

Temporary  stars,  75,  109. 

Tennyson,  Quotations  from,  100. 

Ternary  stars,  57. 

Theophrastus,  hislidea  of  the  Milky 

Way,  135. 
Thomson,  Quotations  from,  100. 
Time,  Measurement  of,  9. 
Toucan  (constellation),  152. 

globular  cluster  in,  in. 

Trapezium  in  Orion,  62. 
Triangulum  (constellation),  151. 

Australe  (constellation),  152. 

Triple  stars,  60. 

Tycho  Brahe,  77. 

Types,  Seech i's  four,  140,  147. 

,U. 

Ursa  Major  (constellation),  14,  29,  31. 

planetary  nebula  57  M  in,  119. 

Ursa  Minor  (constellation),  31. 

V. 

Variable  stars,  83,  145,  146. 

nebulae,  alleged,  129. 

Vega  (a  Lyrae),  24,  25,  34. 

Vertical,  t6. 

Virgo  (constellation),  33,  35. 

Vitruvius  cited,  15. 

Vogel,  140,  145. 

Volans  a/ias  Piscis  Volans  (constel. 

lation),  151. 
Vulpecula  (constellation),  152. 
"  Dumb-bell"  Nebula  in,  127. 

W. 

"Watling     Street,"    name    of    the 

Milky  Way,  136. 
"Way    to    St.   James's,      name    of 

Milky  Way,  136. 
Webb,  Rev.  T.  W     108,  109. 
Whirlpool  or  Spiral  Nebulae,  117. 
Williams,  J.,  77- 
Wolf-Rayet  stars,  141. 
Wordsworth,  Quotations  from,  100. 
Wright,  T,,  134. 

Y. 

Young,  C.  A.,  74,  84. 

(Poet),  Quotations  from,  98. 

Z. 

Zenith,  16. 

Zodiac,  Signs  of,  37. 


(6) 


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UC  SOUTHERN  REGIONAL  LIBRARY  FACILITY 


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